{"id":18342,"date":"2026-07-19T02:26:15","date_gmt":"2026-07-18T17:26:15","guid":{"rendered":"https:\/\/genai-ai.co.jp\/ai-kanri\/?p=18342"},"modified":"2026-07-19T02:26:15","modified_gmt":"2026-07-18T17:26:15","slug":"cc-sql-null-guide","status":"publish","type":"post","link":"https:\/\/genai-ai.co.jp\/ai-kanri\/blog\/cc-sql-null-guide\/","title":{"rendered":"\u30102026\u5e747\u6708\u6700\u65b0\u3011SQL\u306eNULL\u5b8c\u5168\u89e3\u8aac\uff5cIS NULL\u30fbISNULL\u30fbCOALESCE\u30fbNVL\u3092\u696d\u52d9\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3067\u4f7f\u3044\u3053\u306a\u3059"},"content":{"rendered":"\n<style>\n.g-flow-row{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;align-items:center;}\n.g-flow-item{background:linear-gradient(135deg,#1a1a1a,#2a1015);color:#fff;border-radius:8px;padding:16px 14px;min-width:130px;flex:1;text-align:center;}\n.g-flow-arrow{color:#dc2626;font-size:20px;font-weight:700;}\n.g-card-row{display:flex;gap:12px;flex-wrap:wrap;margin:0 0 32px;}\n.g-card-row>div{flex:1;min-width:220px;}\n@media(max-width:600px){\n  .g-flow-row{flex-direction:column;}\n  .g-flow-arrow{transform:rotate(90deg);}\n  .g-card-row{flex-direction:column;}\n  .g-card-row>div{min-width:100%;}\n}\n<\/style>\n\n\n\n<div style=\"margin:0 0 32px;\">\n  <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/07\/thumb-cc-sql-null-guide.jpg\" alt=\"\u30102026\u5e747\u6708\u6700\u65b0\u3011SQL\u306eNULL\u5b8c\u5168\u89e3\u8aac\uff5cIS NULL\u30fbISNULL\u30fbCOALESCE\u30fbNVL\u3092\u696d\u52d9\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3067\u4f7f\u3044\u3053\u306a\u3059\" style=\"width:100%;height:auto;border-radius:12px;display:block;\">\n<\/div>\n\n\n\n<div style=\"background:#f8f9fa;border-radius:12px;padding:24px 28px;margin:0 0 32px;border-left:4px solid #dc2626;\">\n  <p style=\"font-size:15px;font-weight:700;color:#1a1a1a;margin:0 0 16px;\">\u3053\u306e\u8a18\u4e8b\u306e\u5185\u5bb9<\/p>\n  <ol style=\"margin:0;padding-left:20px;font-size:14px;line-height:2.2;list-style:none;\">\n    <li><a href=\"#sec-01\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">01<\/span>SQL\u306eNULL\u3068\u306f\u4f55\u304b\u2015\u2015\u5024\u304c\u300c\u5b58\u5728\u3057\u306a\u3044\u300d\u3053\u3068\u306e\u610f\u5473<\/a><\/li>\n    <li><a href=\"#sec-02\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">02<\/span>IS NULL\u6f14\u7b97\u5b50\u306e\u4f7f\u3044\u65b9<\/a><\/li>\n    <li><a href=\"#sec-03\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">03<\/span>IS NOT NULL\u6f14\u7b97\u5b50\u306e\u4f7f\u3044\u65b9<\/a><\/li>\n    <li><a href=\"#sec-04\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">04<\/span>NULL\u7f6e\u63db\u95a2\u6570\u306e\u5b8c\u5168\u6bd4\u8f03\uff08ISNULL\u30fbCOALESCE\u30fbNVL\u30fbIFNULL\uff09<\/a><\/li>\n    <li><a href=\"#sec-05\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">05<\/span>\u96c6\u8a08\u95a2\u6570\u3068NULL\u2015\u2015COUNT\u30fbSUM\u30fbAVG\u306e\u843d\u3068\u3057\u7a74<\/a><\/li>\n    <li><a href=\"#sec-06\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">06<\/span>CASE\u5f0f\u3067NULL\u3092\u67d4\u8edf\u306b\u5236\u5fa1\u3059\u308b<\/a><\/li>\n    <li><a href=\"#sec-07\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">07<\/span>NULL\u306b\u95a2\u3059\u308b\u3088\u304f\u3042\u308b\u7f60\u3068\u30d0\u30b0\u30d1\u30bf\u30fc\u30f3<\/a><\/li>\n    <li><a href=\"#sec-08\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">08<\/span>Claude Code\u3067SQL\u30af\u30a8\u30ea\u3092\u81ea\u52d5\u751f\u6210\u3059\u308b<\/a><\/li>\n    <li><a href=\"#sec-09\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">09<\/span>\u307e\u3068\u3081<\/a><\/li>\n    <li><a href=\"#faq\" style=\"color:#495057;text-decoration:none;\"><span style=\"color:#dc2626;font-weight:700;margin-right:8px;\">FAQ<\/span>\u3088\u304f\u3042\u308b\u8cea\u554f<\/a><\/li>\n  <\/ol>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u300cSQL\u3067NULL\u304c\u7d61\u3080\u3068\u3046\u307e\u304f\u52d5\u304b\u306a\u3044\u300d\u300cIS NULL\u3068ISNULL\u95a2\u6570\u306e\u9055\u3044\u304c\u5206\u304b\u3089\u306a\u3044\u300d\u300cCOALESCE\u3068NVL\u306f\u3069\u3046\u9055\u3046\u306e\uff1f\u300d\u2014\u2014\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3092\u6271\u3046\u3088\u3046\u306b\u306a\u308b\u3068\u3001NULL\u306e\u58c1\u306b\u5fc5\u305a\u3076\u3064\u304b\u308a\u307e\u3059\u3002NULL\u306f\u300c\u5024\u304c\u306a\u3044\u300d\u3068\u3044\u3046\u72b6\u614b\u3092\u8868\u3059\u7279\u6b8a\u306a\u6982\u5ff5\u3067\u3001\u901a\u5e38\u306e\u5024\uff080\u3084\u7a7a\u6587\u5b57\u306a\u3069\uff09\u3068\u306f\u5168\u304f\u7570\u306a\u308b\u6271\u3044\u304c\u5fc5\u8981\u3067\u3059\u3002\u3053\u306e\u300c\u7279\u6b8a\u306a\u6271\u3044\u300d\u3092\u77e5\u3089\u306a\u3044\u307e\u307e\u9032\u3081\u308b\u3068\u3001\u691c\u7d22\u7d50\u679c\u304c\u6b63\u3057\u304f\u51fa\u306a\u304b\u3063\u305f\u308a\u3001\u96c6\u8a08\u5024\u304c\u4e88\u60f3\u5916\u306e\u6570\u5b57\u306b\u306a\u3063\u305f\u308a\u3068\u3044\u3046\u30d0\u30b0\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001SQL\u306eNULL\u51e6\u7406\u3092\u5b8c\u5168\u306b\u89e3\u8aac\u3057\u307e\u3059\u3002IS NULL\u6f14\u7b97\u5b50\u306b\u3088\u308bNULL\u5224\u5b9a\u3001IS NOT NULL\u3001ISNULL\u95a2\u6570\u30fbCOALESCE\u95a2\u6570\u30fbNVL\u95a2\u6570\u30fbIFNULL\u95a2\u6570\u306e\u74b0\u5883\u5225\u4f7f\u3044\u5206\u3051\u3001\u96c6\u8a08\u95a2\u6570\u3068NULL\u306e\u843d\u3068\u3057\u7a74\u3001CASE\u5f0f\u3092\u4f7f\u3063\u305f\u67d4\u8edf\u306aNULL\u5236\u5fa1\u3001\u305d\u3057\u3066\u3088\u304f\u3042\u308bNULL\u30d0\u30b0\u306e\u30d1\u30bf\u30fc\u30f3\u3068\u5bfe\u7b56\u307e\u3067\u3001\u696d\u52d9\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3067\u5373\u4f7f\u3048\u308b\u30ec\u30d9\u30eb\u3067\u6574\u7406\u3057\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"balloon-wrap\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/ceo-sugasawa.jpg\" alt=\"\u4ee3\u8868\u83c5\u6fa4\">\n    <span class=\"balloon-name\">\u4ee3\u8868\u83c5\u6fa4<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u5f0a\u793e\u3067\u306f\u793e\u5185\u306e\u30c7\u30fc\u30bf\u5206\u6790\u30fb\u58f2\u4e0a\u96c6\u8a08\u30fb\u9867\u5ba2\u7ba1\u7406\u3092\u3059\u3079\u3066SQL\u3067\u56de\u3057\u3066\u3044\u307e\u3059\u3002NULL\u306e\u6271\u3044\u3092\u9593\u9055\u3048\u3066\u300c\u58f2\u4e0a\u5408\u8a08\u304c\u5b9f\u969b\u3088\u308a\u5c11\u306a\u304f\u51fa\u305f\u300d\u3068\u3044\u3046\u7d4c\u9a13\u304c\u3042\u308a\u307e\u3059\u3002NULL\u306f\u5730\u5473\u306b\u898b\u3048\u3066\u3001\u96c6\u8a08\u30af\u30a8\u30ea\u306e\u6b63\u78ba\u6027\u306b\u76f4\u7d50\u3059\u308b\u91cd\u8981\u306a\u6982\u5ff5\u3067\u3059\u3002<\/div>\n<\/div>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u7279\u306bCOALESCE\u95a2\u6570\u306f\u300cNULL\u30920\u306b\u7f6e\u63db\u3057\u3066\u96c6\u8a08\u3059\u308b\u300d\u696d\u52d9\u3067\u306f\u6bce\u56de\u4f7f\u3044\u307e\u3059\u3002\u307e\u305f\u300c= NULL\u304c\u52b9\u304b\u306a\u3044\u300d\u3068\u3044\u3046\u521d\u6b69\u7684\u306a\u7f60\u306f\u591a\u304f\u306e\u65b9\u304c\u4e00\u5ea6\u8e0f\u3080\u306e\u3067\u3001\u6700\u521d\u306b\u4ed5\u7d44\u307f\u3092\u7406\u89e3\u3057\u3066\u304a\u304f\u3053\u3068\u304c\u5927\u5207\u3067\u3059\u3002<\/div>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u306e\u8a18\u4e8b\u3092\u6700\u5f8c\u307e\u3067\u8aad\u3080\u3068\u3001\u6b21\u306e\u3053\u3068\u304c\u5206\u304b\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#fafafa;border-radius:8px;padding:16px 20px;margin:16px 0;border-left:4px solid #dc2626;\">\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span><strong>NULL\u306e\u672c\u8cea<\/strong>\uff1a0\u3084\u7a7a\u6587\u5b57\u3068\u4f55\u304c\u9055\u3046\u306e\u304b\u3001\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3067\u3069\u3046\u683c\u7d0d\u3055\u308c\u308b\u304b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span><strong>IS NULL \/ IS NOT NULL<\/strong>\uff1aNULL\u5224\u5b9a\u306e\u6b63\u3057\u3044\u66f8\u304d\u65b9\u3068\uff1dNULL\u6bd4\u8f03\u304cNG\u306a\u7406\u7531<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span><strong>ISNULL\u30fbCOALESCE\u30fbNVL\u30fbIFNULL<\/strong>\uff1a\u74b0\u5883\u3054\u3068\u306eNULL\u7f6e\u63db\u95a2\u6570\u306e\u4f7f\u3044\u5206\u3051\u5b8c\u5168\u30de\u30c3\u30d7<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span><strong>\u96c6\u8a08\u95a2\u6570\u306e\u843d\u3068\u3057\u7a74<\/strong>\uff1aCOUNT(*)\u3068COUNT(\u5217\u540d)\u306e\u9055\u3044\u3001AVG\u304cNULL\u3092\u7121\u8996\u3059\u308b\u4ed5\u7d44\u307f<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span><strong>CASE\u5f0f\u306eNULL\u5236\u5fa1<\/strong>\uff1a\u6761\u4ef6\u5206\u5c90\u3067NULL\u3092\u81ea\u5728\u306b\u6271\u3046\u30c6\u30af\u30cb\u30c3\u30af<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span><strong>NULL\u30d0\u30b0\u306e\u30d1\u30bf\u30fc\u30f3<\/strong>\uff1a\u696d\u52d9\u3067\u983b\u51fa\u3059\u308bNULL\u8d77\u56e0\u306e\u30d0\u30b0\u3068\u9632\u5fa1\u7684\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0<\/span><\/div>\n\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-01\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">01<\/span>\n  <span class=\"section-label\" style=\"display:block;\">NULL BASICS<\/span>\n  <span class=\"section-title\" style=\"display:block;\">SQL\u306eNULL\u3068\u306f\u4f55\u304b\u2015\u2015\u5024\u304c\u300c\u5b58\u5728\u3057\u306a\u3044\u300d\u3053\u3068\u306e\u610f\u5473<\/span>\n  <span class=\"section-desc\">0\u30fb\u7a7a\u6587\u5b57\u3068\u306e\u9055\u3044\u3001\u4e09\u5024\u8ad6\u7406\u3001\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u3067\u306e\u683c\u7d0d\u306e\u4ed5\u7d44\u307f<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SQL\u306b\u304a\u3051\u308bNULL\u3068\u306f\u3001\u300c\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u30fb\u4e0d\u660e\u30fb\u9069\u7528\u4e0d\u53ef\u80fd\u300d\u3068\u3044\u3046\u72b6\u614b\u3092\u8868\u3059\u7279\u6b8a\u306a\u30de\u30fc\u30ab\u30fc\u3067\u3059\u3002\u6570\u5024\u306e0\u3084\u6587\u5b57\u5217\u306e\u7a7a\u6587\u5b57\uff08\"\"\uff09\u3068\u306f\u5168\u304f\u5225\u7269\u3067\u3059\u3002\u305f\u3068\u3048\u3070\u9867\u5ba2\u30c6\u30fc\u30d6\u30eb\u306e\u300c\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u300d\u5217\u306bNULL\u304c\u5165\u3063\u3066\u3044\u308b\u306a\u3089\u300c\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u3092\u767b\u9332\u3057\u3066\u3044\u306a\u3044\u300d\u3053\u3068\u3092\u610f\u5473\u3057\u3001\u7a7a\u6587\u5b57\"\"\u306a\u3089\u300c\u767b\u9332\u306f\u3057\u305f\u304c\u4e2d\u8eab\u304c\u7a7a\u300d\u3068\u3044\u3046\u9055\u3044\u306b\u306a\u308a\u307e\u3059\u3002\u3053\u306e\u533a\u5225\u304c\u30c7\u30fc\u30bf\u306e\u6b63\u78ba\u6027\u306b\u76f4\u7d50\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#f8f9fa;border-left:4px solid #6b7280;border-radius:0 8px 8px 0;padding:16px 20px;margin:20px 0;\">\n  <p style=\"margin:0 0 4px;font-size:13px;font-weight:700;color:#6b7280;letter-spacing:1px;\">&#128218; \u7528\u8a9e\u89e3\u8aac<\/p>\n  <p style=\"margin:0;font-size:15px;line-height:1.7;\"><strong>NULL\uff08\u30cc\u30eb\uff09<\/strong>\uff1aSQL\u306b\u304a\u3044\u3066\u30c7\u30fc\u30bf\u304c\u300c\u5b58\u5728\u3057\u306a\u3044\u300d\u300c\u4e0d\u660e\u300d\u300c\u672a\u5165\u529b\u300d\u3067\u3042\u308b\u3053\u3068\u3092\u8868\u3059\u7279\u6b8a\u306a\u5024\u3002\u6570\u5024\u306e0\u3084\u7a7a\u6587\u5b57\"\"\u3068\u306f\u7570\u306a\u308b\u6982\u5ff5\u3067\u3059\u3002NULL\u306f\u300c\u5024\u304c\u672a\u5b9a\u7fa9\u300d\u3067\u3042\u308b\u3053\u3068\u3092\u793a\u3059\u305f\u3081\u3001\u901a\u5e38\u306e\u6bd4\u8f03\u6f14\u7b97\uff08=\u3001<>\uff09\u3067\u306fNULL\u3092\u691c\u51fa\u3067\u304d\u305a\u3001\u5c02\u7528\u306eIS NULL\u6f14\u7b97\u5b50\u304c\u5fc5\u8981\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">NULL\u306e\u6700\u5927\u306e\u7279\u5fb4\u306f\u300c\u901a\u5e38\u306e\u6bd4\u8f03\u6f14\u7b97\u304c\u52b9\u304b\u306a\u3044\u300d\u70b9\u3067\u3059\u3002SQL\u3067\u306f\u300c\u5217 = NULL\u300d\u3068\u3044\u3046\u6761\u4ef6\u5f0f\u306f\u5e38\u306bFALSE\u3067\u306f\u306a\u304f\u3001UNKNOWN\uff08\u4e0d\u660e\uff09\u3068\u3044\u3046\u7b2c3\u306e\u72b6\u614b\u3092\u8fd4\u3057\u307e\u3059\u3002\u3053\u308c\u3092SQL\u306e\u300c\u4e09\u5024\u8ad6\u7406\u300d\u3068\u547c\u3073\u307e\u3059\u3002WHERE\u53e5\u3067UNKNOWN\u304c\u8fd4\u3063\u305f\u884c\u306f\u7d50\u679c\u30bb\u30c3\u30c8\u306b\u542b\u307e\u308c\u307e\u305b\u3093\u3002\u300c= NULL\u300d\u3067NULL\u3092\u691c\u51fa\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u4f55\u3082\u8fd4\u3063\u3066\u3053\u306a\u3044\u306e\u306f\u3001\u3053\u306e\u4e09\u5024\u8ad6\u7406\u306e\u4ed5\u7d44\u307f\u306b\u3088\u308b\u3082\u306e\u3067\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#f8f9fa;border-left:4px solid #6b7280;border-radius:0 8px 8px 0;padding:16px 20px;margin:20px 0;\">\n  <p style=\"margin:0 0 4px;font-size:13px;font-weight:700;color:#6b7280;letter-spacing:1px;\">&#128218; \u7528\u8a9e\u89e3\u8aac<\/p>\n  <p style=\"margin:0;font-size:15px;line-height:1.7;\"><strong>\u4e09\u5024\u8ad6\u7406\uff08Three-valued logic\uff09<\/strong>\uff1aSQL\u306e\u6bd4\u8f03\u6f14\u7b97\u306e\u7d50\u679c\u304cTRUE\u30fbFALSE\u30fbUNKNOWN\uff08\u4e0d\u660e\uff09\u306e3\u7a2e\u985e\u306b\u306a\u308b\u8ad6\u7406\u4f53\u7cfb\u3002NULL\u304c\u542b\u307e\u308c\u308b\u6bd4\u8f03\uff08NULL = 5\u3001NULL = NULL\u306a\u3069\uff09\u306f\u5e38\u306bUNKNOWN\u3092\u8fd4\u3057\u307e\u3059\u3002WHERE\u53e5\u3067UNKNOWN\u306b\u306a\u3063\u305f\u884c\u306f\u7d50\u679c\u304b\u3089\u9664\u5916\u3055\u308c\u307e\u3059\u3002\u3053\u308c\u3092\u77e5\u3089\u305a\u306b\u300c= NULL\u300d\u3067NULL\u691c\u7d22\u3059\u308b\u3068\u3001\u691c\u7d22\u7d50\u679c\u304c0\u4ef6\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">NULL\u306f\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u306e\u3042\u3089\u3086\u308b\u5834\u9762\u306b\u5f71\u97ff\u3057\u307e\u3059\u3002WHERE\u53e5\u3067\u306e\u691c\u7d22\u3001JOIN\u7d50\u5408\u3001GROUP BY\u306b\u3088\u308b\u96c6\u8a08\u3001ORDER BY\u4e26\u3073\u66ff\u3048\u2014\u2014\u305d\u308c\u305e\u308c\u3067NULL\u304c\u7279\u6b8a\u306a\u6319\u52d5\u3092\u793a\u3057\u307e\u3059\u3002JOIN\u7d50\u5408\u3067\u306f\u3001\u7d50\u5408\u30ad\u30fc\u304cNULL\u306e\u884c\u306f\u4e00\u81f4\u306a\u3057\u3068\u3057\u3066\u6271\u308f\u308c\u307e\u3059\u3002ORDER BY\u3067\u306f\u3001\u591a\u304f\u306eDBMS\u3067NULL\u306fASC\u306e\u5834\u5408\u306b\u6700\u5c0f\u5024\u6271\u3044\uff08\u5148\u982d\u307e\u305f\u306f\u672b\u5c3e\uff09\u306b\u306a\u308a\u307e\u3059\u3002\u3053\u3046\u3057\u305f\u6319\u52d5\u3092\u7406\u89e3\u305b\u305a\u306b\u696d\u52d9SQL\u3092\u66f8\u304f\u3068\u3001\u610f\u56f3\u3057\u306a\u3044\u30c7\u30fc\u30bf\u306e\u6b20\u843d\u3084\u96c6\u8a08\u30df\u30b9\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<table>\n<thead><tr><th>\u6bd4\u8f03\u5bfe\u8c61<\/th><th>NULL\u3068\u306e\u9055\u3044<\/th><th>\u696d\u52d9\u3067\u306e\u5178\u578b\u4f8b<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>\u6570\u5024\u306e0<\/td><td>0\u306f\u300c\u30bc\u30ed\u3068\u3044\u3046\u5024\u304c\u5b58\u5728\u3059\u308b\u300d\u3002NULL\u306f\u300c\u5024\u81ea\u4f53\u304c\u5b58\u5728\u3057\u306a\u3044\u300d<\/td><td>\u58f2\u4e0a0\u5186 vs \u58f2\u4e0a\u672a\u767b\u9332<\/td><\/tr>\n<tr><td>\u7a7a\u6587\u5b57\"\"<\/td><td>\"\"\u306f\u300c\u7a7a\u306e\u6587\u5b57\u5217\u3068\u3044\u3046\u5024\u304c\u5b58\u5728\u3059\u308b\u300d\u3002NULL\u306f\u300c\u5024\u304c\u306a\u3044\u300d<\/td><td>\u96fb\u8a71\u756a\u53f7\u304c\u7a7a\u6b04\uff08\u767b\u9332\u6e08\uff09 vs \u96fb\u8a71\u756a\u53f7\u304c\u672a\u767b\u9332<\/td><\/tr>\n<tr><td>\u30b9\u30da\u30fc\u30b9\" \"<\/td><td>\u30b9\u30da\u30fc\u30b9\u306f1\u6587\u5b57\u306e\u6587\u5b57\u5217\u3002NULL\u306f\u5024\u306e\u4e0d\u5728<\/td><td>\u30b3\u30fc\u30c9\u6b04\u306e\u30b9\u30da\u30fc\u30b9\u57cb\u3081 vs \u672a\u5165\u529b<\/td><\/tr>\n<\/tbody>\n<\/table>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">NULL\u3068\u7a7a\u6587\u5b57\u306e\u533a\u5225\u306f\u3001\u696d\u52d9\u30c7\u30fc\u30bf\u306e\u54c1\u8cea\u7ba1\u7406\u3067\u975e\u5e38\u306b\u91cd\u8981\u3067\u3059\u3002\u300c\u96fb\u8a71\u756a\u53f7\u304cNULL\u300d\u3068\u300c\u96fb\u8a71\u756a\u53f7\u304c\u7a7a\u6587\u5b57\u300d\u3092\u540c\u4e00\u8996\u3059\u308b\u3068\u3001\u300c\u9023\u7d61\u5148\u672a\u767b\u9332\u9867\u5ba2\u300d\u306e\u4ef6\u6570\u304c\u6b63\u78ba\u306b\u51fa\u306a\u304f\u306a\u308a\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-02\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">02<\/span>\n  <span class=\"section-label\" style=\"display:block;\">IS NULL<\/span>\n  <span class=\"section-title\" style=\"display:block;\">IS NULL\u6f14\u7b97\u5b50\u306e\u4f7f\u3044\u65b9<\/span>\n  <span class=\"section-desc\">NULL\u5024\u306e\u884c\u3092\u6b63\u78ba\u306b\u691c\u51fa\u3059\u308b\u305f\u3081\u306e\u552f\u4e00\u306e\u6b63\u3057\u3044\u65b9\u6cd5<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IS NULL\u6f14\u7b97\u5b50\u306f\u3001\u5217\u306e\u5024\u304cNULL\u3067\u3042\u308b\u3053\u3068\u3092\u5224\u5b9a\u3059\u308b\u305f\u3081\u306e\u6f14\u7b97\u5b50\u3067\u3059\u3002\u524d\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u8aac\u660e\u3057\u305f\u3088\u3046\u306b\u3001\u300c= NULL\u300d\u306f\u4e09\u5024\u8ad6\u7406\u306e\u554f\u984c\u3067\u5e38\u306bUNKNOWN\u3092\u8fd4\u3059\u305f\u3081\u4f7f\u3048\u307e\u305b\u3093\u3002NULL\u3092\u691c\u7d22\u3057\u305f\u3044\u5834\u5408\u306f\u5fc5\u305a\u300cIS NULL\u300d\u3092\u4f7f\u3044\u307e\u3059\u3002\u69cb\u6587\u306f\u300c\u5217\u540d IS NULL\u300d\u3067\u3001\u305d\u306e\u5217\u304cNULL\u3067\u3042\u308c\u3070TRUE\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- IS NULL\u306e\u57fa\u672c\u4f8b\n-- \u9867\u5ba2\u30c6\u30fc\u30d6\u30eb\u304b\u3089\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u304c\u672a\u767b\u9332\u306e\u9867\u5ba2\u3092\u53d6\u5f97\nSELECT\n    customer_id,\n    customer_name,\n    phone_number\nFROM\n    customers\nWHERE\n    email IS NULL;\n\n-- \u8907\u6570\u6761\u4ef6\u3068\u7d44\u307f\u5408\u308f\u305b\u308b\u4f8b\uff08\u30e1\u30fc\u30eb\u304cNULL \u304b\u3064 \u96fb\u8a71\u756a\u53f7\u3082\u5165\u3063\u3066\u3044\u308b\uff09\nSELECT\n    customer_id,\n    customer_name\nFROM\n    customers\nWHERE\n    email IS NULL\n    AND phone_number IS NOT NULL;\n\n-- NG\u4f8b\uff1a\u300c= NULL\u300d\u306f\u4f7f\u308f\u306a\u3044\uff08\u5e38\u306b0\u4ef6\u304c\u8fd4\u308b\uff09\n-- SELECT * FROM customers WHERE email = NULL;  -- \u5e38\u306b\u7a7a\u7d50\u679c\n-- SELECT * FROM customers WHERE email &lt;&gt; NULL; -- \u540c\u69d8\u306b\u7a7a\u7d50\u679c<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">2-1. IS NULL\u3092\u4f7f\u3063\u305f\u5b9f\u8df5\u7684\u306a\u30af\u30a8\u30ea\u30d1\u30bf\u30fc\u30f3<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u696d\u52d9DB\u3067IS NULL\u304c\u6700\u3082\u3088\u304f\u4f7f\u308f\u308c\u308b\u306e\u306f\u300c\u30c7\u30fc\u30bf\u4e0d\u5099\u306e\u691c\u51fa\u300d\u3067\u3059\u3002\u5165\u529b\u30d5\u30a9\u30fc\u30e0\u304b\u3089\u767b\u9332\u3055\u308c\u305f\u30c7\u30fc\u30bf\u306b\u5fc5\u9808\u9805\u76ee\u304c\u6f0f\u308c\u3066\u3044\u306a\u3044\u304b\u78ba\u8a8d\u3059\u308b\u3001\u30d0\u30c3\u30c1\u51e6\u7406\u3067\u672a\u51e6\u7406\u30ec\u30b3\u30fc\u30c9\u3092\u62bd\u51fa\u3059\u308b\u3001\u30de\u30b9\u30bf\u30fc\u30c7\u30fc\u30bf\u3068\u306e\u7d50\u5408\u3067\u672a\u7d10\u4ed8\u3051\u30ec\u30b3\u30fc\u30c9\u3092\u6d17\u3044\u51fa\u3059\u2014\u2014\u3053\u3046\u3057\u305f\u54c1\u8cea\u30c1\u30a7\u30c3\u30af\u306eSQL\u5168\u822c\u3067IS NULL\u304c\u6d3b\u8e8d\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- \u5b9f\u8df5\u30d1\u30bf\u30fc\u30f31\uff1a\u30c7\u30fc\u30bf\u4e0d\u5099\u30c1\u30a7\u30c3\u30af\uff08\u8907\u6570\u5217\u306eNULL\u3092\u4e00\u62ec\u78ba\u8a8d\uff09\nSELECT\n    customer_id,\n    customer_name,\n    CASE WHEN email IS NULL THEN &#x27;\u672a\u767b\u9332&#x27; ELSE &#x27;\u767b\u9332\u6e08&#x27; END AS email_status,\n    CASE WHEN phone_number IS NULL THEN &#x27;\u672a\u767b\u9332&#x27; ELSE &#x27;\u767b\u9332\u6e08&#x27; END AS phone_status,\n    CASE WHEN address IS NULL THEN &#x27;\u672a\u767b\u9332&#x27; ELSE &#x27;\u767b\u9332\u6e08&#x27; END AS address_status\nFROM\n    customers\nWHERE\n    email IS NULL\n    OR phone_number IS NULL\n    OR address IS NULL\nORDER BY\n    customer_id;\n\n-- \u5b9f\u8df5\u30d1\u30bf\u30fc\u30f32\uff1aLEFT JOIN\u3067\u7d50\u5408\u3067\u304d\u306a\u304b\u3063\u305f\u884c\u3092\u62bd\u51fa\uff08\u5b64\u7acb\u30ec\u30b3\u30fc\u30c9\u691c\u51fa\uff09\nSELECT\n    o.order_id,\n    o.customer_id\nFROM\n    orders o\n    LEFT JOIN customers c ON o.customer_id = c.customer_id\nWHERE\n    c.customer_id IS NULL;  -- JOIN\u3067\u304d\u306a\u304b\u3063\u305f = \u9867\u5ba2\u30de\u30b9\u30bf\u30fc\u306b\u5b58\u5728\u3057\u306a\u3044\u6ce8\u6587<\/pre>\n<\/div>\n\n\n\n<div style=\"background:#f0fdf4;border:1px solid #22c55e;border-radius:8px;padding:20px 24px;margin:24px 0;\">\n  <div style=\"display:flex;align-items:center;gap:8px;margin-bottom:12px;\">\n    <span style=\"font-size:18px;\">&#128161;<\/span>\n    <strong style=\"color:#16a34a;font-size:15px;\">LEFT JOIN\u3067\u306eIS NULL\u306f\u300c\u5b58\u5728\u3057\u306a\u3044\u884c\u306e\u691c\u51fa\u300d\u306b\u6700\u9069<\/strong>\n  <\/div>\n  <p style=\"margin:0;font-size:15px;line-height:1.8;color:#333;\">\u30c6\u30fc\u30d6\u30ebA\u306b\u5b58\u5728\u3059\u308b\u304c\u30c6\u30fc\u30d6\u30ebB\u306b\u5b58\u5728\u3057\u306a\u3044\u30ec\u30b3\u30fc\u30c9\u3092\u63a2\u3059\u51e6\u7406\u306f\u3001LEFT JOIN + WHERE B.key IS NULL\u306e\u30d1\u30bf\u30fc\u30f3\u304c\u5b9a\u77f3\u3067\u3059\u3002NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u3088\u308a\u76f4\u611f\u7684\u3067\u3001NULL\u3092\u542b\u3080\u5834\u5408\u306e\u6319\u52d5\u3082\u5b89\u5b9a\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n\n<div class=\"balloon-wrap\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/ceo-sugasawa.jpg\" alt=\"\u4ee3\u8868\u83c5\u6fa4\">\n    <span class=\"balloon-name\">\u4ee3\u8868\u83c5\u6fa4<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u5f0a\u793e\u3067\u306f\u6708\u6b21\u306e\u53d7\u6ce8\u30c7\u30fc\u30bf\u6574\u5408\u6027\u30c1\u30a7\u30c3\u30afSQL\u3092Claude Code\u3067\u81ea\u52d5\u751f\u6210\u3055\u305b\u3066\u3044\u307e\u3059\u3002\u300c\u9867\u5ba2ID\u304c\u9867\u5ba2\u30de\u30b9\u30bf\u30fc\u306b\u5b58\u5728\u3057\u306a\u3044\u6ce8\u6587\u30c7\u30fc\u30bf\u3092\u691c\u51fa\u3059\u308b\u300d\u3068\u3044\u3046\u8981\u4ef6\u3092\u8aac\u660e\u3059\u308b\u3068\u3001LEFT JOIN + IS NULL\u306e\u30d1\u30bf\u30fc\u30f3\u3092\u5373\u5ea7\u306b\u751f\u6210\u3057\u3066\u304f\u308c\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-03\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">03<\/span>\n  <span class=\"section-label\" style=\"display:block;\">IS NOT NULL<\/span>\n  <span class=\"section-title\" style=\"display:block;\">IS NOT NULL\u6f14\u7b97\u5b50\u306e\u4f7f\u3044\u65b9<\/span>\n  <span class=\"section-desc\">NULL\u4ee5\u5916\u306e\u884c\u3092\u62bd\u51fa\u3059\u308b\u9006\u6761\u4ef6\u3068\u3001NOT\u306e\u4f4d\u7f6e\u306b\u6ce8\u610f\u3059\u3079\u304d\u70b9<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IS NOT NULL\u6f14\u7b97\u5b50\u306f\u3001IS NULL\u306e\u9006\u3067\u300cNULL\u4ee5\u5916\u306e\u5024\u304c\u5b58\u5728\u3059\u308b\u300d\u884c\u3092\u62bd\u51fa\u3057\u307e\u3059\u3002\u300c\u5024\u304c\u5165\u529b\u3055\u308c\u3066\u3044\u308b\u30ec\u30b3\u30fc\u30c9\u3060\u3051\u51e6\u7406\u3057\u305f\u3044\u300d\u300c\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u304c\u767b\u9332\u6e08\u307f\u306e\u9867\u5ba2\u306b\u3060\u3051\u9001\u4fe1\u3059\u308b\u300d\u3068\u3044\u3063\u305f\u5834\u9762\u3067\u4f7f\u3044\u307e\u3059\u3002\u69cb\u6587\u306f\u300c\u5217\u540d IS NOT NULL\u300d\u3067\u3001\u5024\u304cNULL\u3067\u306a\u3051\u308c\u3070TRUE\u3092\u8fd4\u3057\u307e\u3059\u3002\u300cNOT (\u5217\u540d IS NULL)\u300d\u3068\u7b49\u4fa1\u3067\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- IS NOT NULL\u306e\u57fa\u672c\u4f8b\n-- \u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u304c\u767b\u9332\u6e08\u307f\u306e\u9867\u5ba2\u306e\u307f\u53d6\u5f97\nSELECT\n    customer_id,\n    customer_name,\n    email\nFROM\n    customers\nWHERE\n    email IS NOT NULL;\n\n-- \u8907\u6570\u6761\u4ef6\uff1a\u96fb\u8a71\u30fb\u30e1\u30fc\u30eb\u4e21\u65b9\u304c\u5165\u529b\u6e08\u307f\u306e\u9867\u5ba2\nSELECT\n    customer_id,\n    customer_name\nFROM\n    customers\nWHERE\n    email IS NOT NULL\n    AND phone_number IS NOT NULL;\n\n-- \u6ce8\u6587\u306b\u5bfe\u3057\u3066\u62c5\u5f53\u8005\u304c\u5272\u308a\u5f53\u3066\u3089\u308c\u3066\u3044\u308b\u3082\u306e\nSELECT\n    order_id,\n    order_date,\n    assigned_staff\nFROM\n    orders\nWHERE\n    assigned_staff IS NOT NULL\nORDER BY\n    order_date DESC;<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">3-1. IS NOT NULL\u3068NULL\u6392\u9664\u306e\u8003\u3048\u65b9<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u696d\u52d9\u30af\u30a8\u30ea\u3067\u91cd\u8981\u306a\u306e\u306f\u3001\u96c6\u8a08\u30fb\u5206\u6790\u7cfb\u306eSQL\u3067NULL\u3092\u610f\u56f3\u7684\u306b\u6392\u9664\u3059\u308b\u304b\u3069\u3046\u304b\u3092\u660e\u793a\u7684\u306b\u6c7a\u65ad\u3059\u308b\u3053\u3068\u3067\u3059\u3002\u305f\u3068\u3048\u3070\u300c\u767b\u9332\u6e08\u307f\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u306e\u4ef6\u6570\u300d\u3092\u96c6\u8a08\u3059\u308b\u3068\u304d\u3001WHERE email IS NOT NULL \u3092\u4ed8\u3051\u308b\u304b\u3069\u3046\u304b\u3067\u7d50\u679c\u304c\u5909\u308f\u308a\u307e\u3059\u3002\u5f8c\u8ff0\u3059\u308bCOUNT\u95a2\u6570\u306e\u6319\u52d5\u3068\u5408\u308f\u305b\u3066\u7406\u89e3\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- NULL\u6392\u9664\u306e\u96c6\u8a08\u4f8b\n-- \u5168\u9867\u5ba2\u6570\nSELECT COUNT(*) AS total_customers FROM customers;\n\n-- \u30e1\u30fc\u30eb\u767b\u9332\u6e08\u307f\u306e\u9867\u5ba2\u6570\uff08IS NOT NULL\u3067\u660e\u793a\u7684\u306b\u7d5e\u308a\u8fbc\u3080\uff09\nSELECT COUNT(*) AS email_registered_count\nFROM customers\nWHERE email IS NOT NULL;\n\n-- \u4e0a\u8a18\u3068\u540c\u7b49\u3060\u304c\u3001COUNT(email)\u3067\u3082\u540c\u3058\u7d50\u679c\uff08NULL\u306f\u81ea\u52d5\u9664\u5916\u3055\u308c\u308b\uff09\nSELECT COUNT(email) AS email_registered_count\nFROM customers;\n\n-- \u30e1\u30fc\u30eb\u672a\u767b\u9332\u7387\u306e\u8a08\u7b97\nSELECT\n    COUNT(*) AS total,\n    SUM(CASE WHEN email IS NULL THEN 1 ELSE 0 END) AS null_count,\n    ROUND(\n        SUM(CASE WHEN email IS NULL THEN 1 ELSE 0 END) * 100.0 \/ COUNT(*),\n        1\n    ) AS null_rate_percent\nFROM customers;<\/pre>\n<\/div>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">IS NOT NULL\u306fWHERE\u53e5\u3067\u3088\u304f\u4f7f\u3044\u307e\u3059\u304c\u3001CASE\u5f0f\u3068\u306e\u7d44\u307f\u5408\u308f\u305b\u3067NULL\u7387\u306e\u8a08\u7b97\u304c\u3067\u304d\u307e\u3059\u3002\u300c\u5fc5\u9808\u9805\u76ee\u306e\u5165\u529b\u7387\u30ec\u30dd\u30fc\u30c8\u300d\u306e\u3088\u3046\u306a\u30c7\u30fc\u30bf\u54c1\u8cea\u30c0\u30c3\u30b7\u30e5\u30dc\u30fc\u30c9\u3092\u4f5c\u308b\u3068\u304d\u91cd\u5b9d\u3059\u308b\u30d1\u30bf\u30fc\u30f3\u3067\u3059\u3002<\/div>\n<\/div>\n\n\n\n<div style=\"background:#fafafa;border-radius:8px;padding:16px 20px;margin:16px 0;border-left:4px solid #dc2626;\">\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NULL\u884c\u3092\u62bd\u51fa\u3057\u305f\u3044\uff1aWHERE \u5217\u540d IS NULL<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NULL\u4ee5\u5916\u3092\u62bd\u51fa\u3057\u305f\u3044\uff1aWHERE \u5217\u540d IS NOT NULL<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u300c= NULL\u300d\u300c<> NULL\u300d\u306f\u4f7f\u7528\u7981\u6b62\uff08\u4e09\u5024\u8ad6\u7406\u3067UNKNOWN\u306b\u306a\u308b\uff09<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u3092NULL\u542b\u307f\u30c7\u30fc\u30bf\u306b\u4f7f\u3046\u3068\u5168\u4ef6\u9664\u5916\u3055\u308c\u308b\u5371\u967a\u304c\u3042\u308b\uff08Section 07\u53c2\u7167\uff09<\/span><\/div>\n\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-04\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">04<\/span>\n  <span class=\"section-label\" style=\"display:block;\">NULL REPLACE FUNCTIONS<\/span>\n  <span class=\"section-title\" style=\"display:block;\">NULL\u7f6e\u63db\u95a2\u6570\u306e\u5b8c\u5168\u6bd4\u8f03\uff08ISNULL\u30fbCOALESCE\u30fbNVL\u30fbIFNULL\uff09<\/span>\n  <span class=\"section-desc\">\u74b0\u5883\uff08SQL Server\u30fbOracle\u30fbMySQL\u30fbPostgreSQL\uff09\u3054\u3068\u306e\u4f7f\u3044\u5206\u3051\u30de\u30c3\u30d7<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">NULL\u5024\u304c\u542b\u307e\u308c\u308b\u5217\u3092\u96c6\u8a08\u3084\u8868\u793a\u306b\u4f7f\u3046\u5834\u5408\u3001NULL\u3092\u5225\u306e\u5024\uff080\u3084\u7a7a\u6587\u5b57\u306a\u3069\uff09\u306b\u7f6e\u63db\u3057\u3066\u304b\u3089\u51e6\u7406\u3059\u308b\u306e\u304c\u57fa\u672c\u3067\u3059\u3002\u3053\u306e\u300cNULL\u7f6e\u63db\u300d\u306e\u95a2\u6570\u306fDBMS\u306b\u3088\u3063\u3066\u7570\u306a\u308a\u307e\u3059\u3002SQL Server\u306fISNULL\u95a2\u6570\u3001Oracle\u306fNVL\u95a2\u6570\u3001MySQL\u306fIFNULL\u95a2\u6570\u3001\u305d\u3057\u3066\u5168DBMS\u3067\u4f7f\u3048\u308b\u306e\u304cCOALESCE\u95a2\u6570\u3067\u3059\u3002\u74b0\u5883\u3054\u3068\u306b\u4f7f\u3046\u95a2\u6570\u304c\u9055\u3046\u305f\u3081\u3001\u8907\u6570\u306eDB\u3092\u6271\u3046\u5834\u9762\u3067\u306f\u6df7\u4e71\u3057\u3084\u3059\u3044\u90e8\u5206\u3067\u3059\u3002<\/p>\n\n\n\n<table>\n<thead><tr><th>\u95a2\u6570\u540d<\/th><th>\u5bfe\u5fdcDBMS<\/th><th>\u69cb\u6587<\/th><th>\u7279\u5fb4<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>ISNULL()<\/td><td>SQL Server\uff08\u4e3b\uff09<\/td><td>ISNULL(\u5217, \u4ee3\u66ff\u5024)<\/td><td>\u5f15\u65702\u3064\u306e\u307f\u3002\u9ad8\u901f\u3060\u304cSQL Server\u5c02\u7528<\/td><\/tr>\n<tr><td>NVL()<\/td><td>Oracle\uff08\u4e3b\uff09<\/td><td>NVL(\u5217, \u4ee3\u66ff\u5024)<\/td><td>\u5f15\u65702\u3064\u306e\u307f\u3002Oracle\u5c02\u7528<\/td><\/tr>\n<tr><td>IFNULL()<\/td><td>MySQL \/ MariaDB<\/td><td>IFNULL(\u5217, \u4ee3\u66ff\u5024)<\/td><td>\u5f15\u65702\u3064\u306e\u307f\u3002MySQL\u7cfb\u5c02\u7528<\/td><\/tr>\n<tr><td>COALESCE()<\/td><td>\u5168DBMS\uff08SQL\u6a19\u6e96\uff09<\/td><td>COALESCE(\u50241, \u50242, ...)<\/td><td>\u5f15\u6570N\u500b\u3002\u6700\u521d\u306e\u975eNULL\u5024\u3092\u8fd4\u3059\u3002\u79fb\u690d\u6027\u25ce<\/td><\/tr>\n<tr><td>NVL2()<\/td><td>Oracle<\/td><td>NVL2(\u5217, NULL\u4ee5\u5916\u306e\u5024, NULL\u306e\u5024)<\/td><td>NULL\u30fb\u975eNULL\u3067\u7570\u306a\u308b\u5024\u3092\u8fd4\u3059\u9ad8\u6a5f\u80fd\u7248<\/td><\/tr>\n<\/tbody>\n<\/table>\n\n\n\n<div style=\"background:#f8f9fa;border-left:4px solid #6b7280;border-radius:0 8px 8px 0;padding:16px 20px;margin:20px 0;\">\n  <p style=\"margin:0 0 4px;font-size:13px;font-weight:700;color:#6b7280;letter-spacing:1px;\">&#128218; \u7528\u8a9e\u89e3\u8aac<\/p>\n  <p style=\"margin:0;font-size:15px;line-height:1.7;\"><strong>COALESCE\uff08\u30b3\u30a2\u30ec\u30b9\uff09\u95a2\u6570<\/strong>\uff1aSQL\u6a19\u6e96\u3067\u898f\u5b9a\u3055\u308c\u305fNULL\u7f6e\u63db\u95a2\u6570\u3002COALESCE(\u50241, \u50242, ..., \u5024N)\u306e\u5f62\u3067\u8907\u6570\u306e\u5f15\u6570\u3092\u53d6\u308a\u3001\u5de6\u304b\u3089\u9806\u306b\u8a55\u4fa1\u3057\u3066\u6700\u521d\u306eNULL\u4ee5\u5916\u306e\u5024\u3092\u8fd4\u3057\u307e\u3059\u3002\u5168\u3066\u306e\u5f15\u6570\u304cNULL\u306e\u5834\u5408\u306e\u307fNULL\u3092\u8fd4\u3057\u307e\u3059\u3002SQL Server\u30fbOracle\u30fbMySQL\u30fbPostgreSQL\u3059\u3079\u3066\u3067\u4f7f\u3048\u308b\u305f\u3081\u3001\u79fb\u690d\u6027\u3092\u91cd\u8996\u3059\u308b\u3068\u304d\u306e\u7b2c\u4e00\u9078\u629e\u3067\u3059\u3002<\/p>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">4-1. COALESCE\u95a2\u6570\u306e\u4f7f\u3044\u65b9\uff08\u5168\u74b0\u5883\u5bfe\u5fdc\uff09<\/h3>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- COALESCE\u95a2\u6570\u306e\u57fa\u672c\u4f8b\n-- 1\u3064\u306e\u5217\u306eNULL\u30920\u306b\u7f6e\u63db\nSELECT\n    product_id,\n    product_name,\n    COALESCE(discount_rate, 0) AS discount_rate  -- NULL\u306a\u30890\u306b\u7f6e\u63db\nFROM\n    products;\n\n-- \u8907\u6570\u5217\u3092\u9806\u306b\u8a66\u3059\uff08\u6700\u521d\u306b\u975eNULL\u306e\u5217\u3092\u4f7f\u3046\uff09\nSELECT\n    customer_id,\n    COALESCE(mobile_phone, home_phone, work_phone, &#x27;\u9023\u7d61\u5148\u306a\u3057&#x27;) AS contact_number\nFROM\n    customers;\n-- mobile_phone\u2192home_phone\u2192work_phone\u306e\u9806\u306b\u975eNULL\u306e\u6700\u521d\u306e\u5024\u3092\u4f7f\u3046\n\n-- \u96c6\u8a08\u3067NULL\u30920\u3068\u3057\u3066\u6271\u3046\uff08\u6700\u91cd\u8981\u30d1\u30bf\u30fc\u30f3\uff09\nSELECT\n    department,\n    SUM(COALESCE(sales_amount, 0)) AS total_sales\nFROM\n    sales\nGROUP BY\n    department;<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">4-2. ISNULL\u95a2\u6570\uff08SQL Server\uff09<\/h3>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- SQL Server\u306eISNULL\u95a2\u6570\n-- \u69cb\u6587\uff1aISNULL(\u78ba\u8a8d\u3059\u308b\u5024, NULL\u306e\u5834\u5408\u306e\u4ee3\u66ff\u5024)\nSELECT\n    employee_id,\n    employee_name,\n    ISNULL(department, &#x27;\u672a\u914d\u5c5e&#x27;) AS department,\n    ISNULL(bonus_amount, 0) AS bonus_amount\nFROM\n    employees;\n\n-- COALESCE vs ISNULL \u306e\u9055\u3044\uff08SQL Server\uff09\n-- ISNULL\u306f\u5f15\u65702\u3064\u306e\u307f\u3002\u8907\u6570\u30d5\u30a9\u30fc\u30eb\u30d0\u30c3\u30af\u304c\u5fc5\u8981\u306a\u3068\u304d\u306fCOALESCE\u3092\u4f7f\u3046\nSELECT\n    ISNULL(col1, &#x27;default&#x27;)     -- OK: \u5f15\u65702\u3064\n    -- ISNULL(col1, col2, &#x27;default&#x27;) -- NG: \u5f15\u65703\u3064\u306f\u30a8\u30e9\u30fc\n    COALESCE(col1, col2, &#x27;default&#x27;) -- OK: \u5f15\u6570N\u500b\nFROM test_table;<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">4-3. NVL\u95a2\u6570\uff08Oracle\uff09<\/h3>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- Oracle\u306eNVL\u95a2\u6570\n-- \u69cb\u6587\uff1aNVL(\u78ba\u8a8d\u3059\u308b\u5024, NULL\u306e\u5834\u5408\u306e\u4ee3\u66ff\u5024)\nSELECT\n    employee_id,\n    NVL(department_name, &#x27;\u672a\u914d\u5c5e&#x27;) AS department_name,\n    NVL(salary, 0) AS salary\nFROM\n    employees;\n\n-- NVL2\u95a2\u6570\uff08NULL\u30fb\u975eNULL\u3067\u7570\u306a\u308b\u5024\u3092\u8fd4\u3059\u9ad8\u6a5f\u80fd\u7248\uff09\n-- \u69cb\u6587\uff1aNVL2(\u5217, NULL\u3067\u306a\u3044\u5834\u5408\u306e\u5024, NULL\u306e\u5834\u5408\u306e\u5024)\nSELECT\n    customer_id,\n    NVL2(email, &#x27;\u30e1\u30fc\u30eb\u767b\u9332\u6e08&#x27;, &#x27;\u30e1\u30fc\u30eb\u672a\u767b\u9332&#x27;) AS email_status\nFROM\n    customers;\n-- email\u304cNULL\u3067\u306a\u3051\u308c\u3070&#x27;\u30e1\u30fc\u30eb\u767b\u9332\u6e08&#x27;\u3001NULL\u306a\u3089&#x27;\u30e1\u30fc\u30eb\u672a\u767b\u9332&#x27;\u3092\u8fd4\u3059<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">4-4. IFNULL\u95a2\u6570\uff08MySQL \/ MariaDB\uff09<\/h3>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- MySQL\u306eIFNULL\u95a2\u6570\n-- \u69cb\u6587\uff1aIFNULL(\u78ba\u8a8d\u3059\u308b\u5024, NULL\u306e\u5834\u5408\u306e\u4ee3\u66ff\u5024)\nSELECT\n    product_id,\n    product_name,\n    IFNULL(stock_quantity, 0) AS stock_quantity,\n    IFNULL(category, &#x27;\u672a\u5206\u985e&#x27;) AS category\nFROM\n    products;\n\n-- MySQL\u3067\u306fCOALESCE\u3082\u4f7f\u3048\u308b\u305f\u3081\u3001\u8907\u6570\u30d5\u30a9\u30fc\u30eb\u30d0\u30c3\u30af\u304c\u5fc5\u8981\u306a\u5834\u5408\u306fCOALESCE\u3092\u63a8\u5968\nSELECT\n    COALESCE(mobile_phone, home_phone, &#x27;\u9023\u7d61\u5148\u306a\u3057&#x27;) AS contact\nFROM customers;<\/pre>\n<\/div>\n\n\n\n<div style=\"background:#f0fdf4;border:1px solid #22c55e;border-radius:8px;padding:20px 24px;margin:24px 0;\">\n  <div style=\"display:flex;align-items:center;gap:8px;margin-bottom:12px;\">\n    <span style=\"font-size:18px;\">&#128161;<\/span>\n    <strong style=\"color:#16a34a;font-size:15px;\">\u79fb\u690d\u6027\u3092\u8003\u616e\u3059\u308b\u306a\u3089\u5e38\u306bCOALESCE\u3092\u4f7f\u3046<\/strong>\n  <\/div>\n  <p style=\"margin:0;font-size:15px;line-height:1.8;color:#333;\">ISNULL\u30fbNVL\u30fbIFNULL\u306f\u305d\u308c\u305e\u308c\u7279\u5b9a\u306eDBMS\u5c02\u7528\u95a2\u6570\u3067\u3059\u3002\u5c06\u6765\u7684\u306bDB\u3092\u79fb\u884c\u3059\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u3001\u307e\u305f\u306f\u8907\u6570DB\u306b\u5bfe\u5fdc\u3057\u305f\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u4f5c\u308b\u5834\u5408\u306f\u3001SQL\u6a19\u6e96\u306eCOALESCE\u306b\u7d71\u4e00\u3059\u308b\u3053\u3068\u3092\u5f37\u304f\u63a8\u5968\u3057\u307e\u3059\u3002\u5f15\u6570\u304c2\u3064\u306e\u5834\u5408\u3082COALESCE(\u5217, \u4ee3\u66ff\u5024)\u3068\u66f8\u3051\u3070\u3001\u3069\u306eDBMS\u3067\u3082\u305d\u306e\u307e\u307e\u52d5\u304d\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n\n<div class=\"balloon-wrap\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/ceo-sugasawa.jpg\" alt=\"\u4ee3\u8868\u83c5\u6fa4\">\n    <span class=\"balloon-name\">\u4ee3\u8868\u83c5\u6fa4<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u5f0a\u793e\u3067\u306fSQL Server\u304b\u3089MySQL\u3078\u306eDB\u79fb\u884c\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3067\u3001ISNULL\u95a2\u6570\u3092COALESCE\u306b\u4e00\u62ec\u7f6e\u63db\u3059\u308b\u4f5c\u696d\u304c\u767a\u751f\u3057\u307e\u3057\u305f\u3002\u6700\u521d\u304b\u3089COALESCE\u3067\u7d71\u4e00\u3057\u3066\u3044\u308c\u3070\u4e0d\u8981\u306a\u4f5c\u696d\u3067\u3057\u305f\u3002\u3053\u306e\u6559\u8a13\u304b\u3089\u3001\u793e\u5185\u3067\u306f\u79fb\u690d\u6027\u3092\u8003\u616e\u3057\u3066COALESCE\u63a8\u5968\u306b\u3057\u3066\u3044\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-05\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">05<\/span>\n  <span class=\"section-label\" style=\"display:block;\">AGGREGATE FUNCTIONS<\/span>\n  <span class=\"section-title\" style=\"display:block;\">\u96c6\u8a08\u95a2\u6570\u3068NULL\u2015\u2015COUNT\u30fbSUM\u30fbAVG\u306e\u843d\u3068\u3057\u7a74<\/span>\n  <span class=\"section-desc\">NULL\u3092\u542b\u3080\u30c7\u30fc\u30bf\u306e\u96c6\u8a08\u3067\u8d77\u304d\u308b\u300c\u30b5\u30a4\u30ec\u30f3\u30c8\u30d0\u30b0\u300d\u3092\u9632\u3050<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">SQL\u306e\u96c6\u8a08\u95a2\u6570\u306fNULL\u3092\u7279\u5225\u306b\u6271\u3044\u307e\u3059\u3002\u96c6\u8a08\u95a2\u6570\u306e\u591a\u304f\u306f\u300cNULL\u3092\u7121\u8996\u3057\u3066\u96c6\u8a08\u3059\u308b\u300d\u3068\u3044\u3046\u4ed5\u69d8\u306b\u306a\u3063\u3066\u3044\u307e\u3059\u304c\u3001\u3053\u306e\u4ed5\u69d8\u304c\u539f\u56e0\u3067\u610f\u56f3\u305b\u305a\u30c7\u30fc\u30bf\u304c\u6b20\u843d\u3059\u308b\u30d0\u30b0\u304c\u767a\u751f\u3057\u307e\u3059\u3002\u300c\u30b5\u30a4\u30ec\u30f3\u30c8\u30d0\u30b0\u300d\u3068\u547c\u3070\u308c\u308b\u3053\u306e\u554f\u984c\u306f\u3001\u7d50\u679c\u304c\u660e\u3089\u304b\u306b\u304a\u304b\u3057\u304f\u306a\u308b\u306e\u3067\u306f\u306a\u304f\u300c\u6570\u5024\u304c\u5c11\u3057\u5c11\u306a\u3044\u300d\u7a0b\u5ea6\u306a\u306e\u3067\u6c17\u3065\u304d\u306b\u304f\u304f\u3001\u696d\u52d9\u30c7\u30fc\u30bf\u306e\u4fe1\u983c\u6027\u3092\u640d\u306a\u3046\u539f\u56e0\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<table>\n<thead><tr><th>\u95a2\u6570<\/th><th>NULL\u306e\u6271\u3044<\/th><th>\u6ce8\u610f\u70b9<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>COUNT(*)<\/td><td>\u5168\u884c\u3092\u30ab\u30a6\u30f3\u30c8\uff08NULL\u3082\u542b\u3080\uff09<\/td><td>\u30c6\u30fc\u30d6\u30eb\u306e\u5168\u884c\u6570\u3092\u8fd4\u3059<\/td><\/tr>\n<tr><td>COUNT(\u5217\u540d)<\/td><td>NULL\u3092\u9664\u3044\u3066\u30ab\u30a6\u30f3\u30c8<\/td><td>\u5217\u306bNULL\u304c\u542b\u307e\u308c\u308b\u3068 COUNT(*) \u3068\u7570\u306a\u308b\u7d50\u679c\u306b\u306a\u308b<\/td><\/tr>\n<tr><td>SUM(\u5217\u540d)<\/td><td>NULL\u3092\u7121\u8996\u3057\u3066\u5408\u7b97<\/td><td>\u5168\u884cNULL\u306e\u5834\u5408\u306fSUM=NULL\uff080\u3067\u306f\u306a\u3044\uff09<\/td><\/tr>\n<tr><td>AVG(\u5217\u540d)<\/td><td>NULL\u3092\u9664\u3044\u305f\u884c\u6570\u3067\u5272\u308b<\/td><td>NULL\u3092\u300c0\u300d\u3068\u6df7\u540c\u3059\u308b\u3068\u5e73\u5747\u5024\u304c\u5909\u308f\u308b<\/td><\/tr>\n<tr><td>MAX\/MIN(\u5217\u540d)<\/td><td>NULL\u3092\u7121\u8996\u3057\u3066\u6700\u5927\u30fb\u6700\u5c0f<\/td><td>NULL\u306f\u6bd4\u8f03\u304b\u3089\u9664\u5916\u3055\u308c\u308b<\/td><\/tr>\n<\/tbody>\n<\/table>\n\n\n\n<div style=\"background:#f8f9fa;border-left:4px solid #6b7280;border-radius:0 8px 8px 0;padding:16px 20px;margin:20px 0;\">\n  <p style=\"margin:0 0 4px;font-size:13px;font-weight:700;color:#6b7280;letter-spacing:1px;\">&#128218; \u7528\u8a9e\u89e3\u8aac<\/p>\n  <p style=\"margin:0;font-size:15px;line-height:1.7;\"><strong>COUNT(*) \u3068 COUNT(\u5217\u540d) \u306e\u9055\u3044<\/strong>\uff1aCOUNT(*)\u306fNULL\u3092\u542b\u3080\u5168\u884c\u3092\u6570\u3048\u307e\u3059\u3002COUNT(\u5217\u540d)\u306f\u6307\u5b9a\u3057\u305f\u5217\u304cNULL\u3067\u306a\u3044\u884c\u3060\u3051\u3092\u6570\u3048\u307e\u3059\u3002\u9867\u5ba2\u30c6\u30fc\u30d6\u30eb\u306b100\u884c\u3042\u3063\u3066email\u304c20\u884cNULL\u306e\u5834\u5408\u3001COUNT(*) = 100\u3001COUNT(email) = 80 \u306b\u306a\u308a\u307e\u3059\u3002\u3053\u306e\u9055\u3044\u3092\u77e5\u3089\u305a\u306b\u4ef6\u6570\u96c6\u8a08\u3059\u308b\u3068\u6b63\u78ba\u306a\u6570\u5024\u304c\u51fa\u307e\u305b\u3093\u3002<\/p>\n<\/div>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- COUNT(*)\u3068COUNT(\u5217\u540d)\u306e\u9055\u3044\n-- \u30b5\u30f3\u30d7\u30eb\u30c7\u30fc\u30bf: \u9867\u5ba25\u4eba\u3001\u30e1\u30fc\u30eb\u767b\u93323\u4eba\uff082\u4eba\u306fNULL\uff09\nSELECT\n    COUNT(*) AS total_rows,           -- 5\uff08\u5168\u884c\uff09\n    COUNT(email) AS email_count,      -- 3\uff08NULL\u3092\u9664\u304f\uff09\n    COUNT(DISTINCT email) AS unique_emails  -- \u91cd\u8907\u9664\u3044\u305f\u30e1\u30fc\u30eb\u6570\nFROM customers;\n\n-- SUM\u3068AVG\u306eNULL\u6319\u52d5\n-- sales_amount\u306b NULL \u304c\u542b\u307e\u308c\u308b\u5834\u5408\nSELECT\n    SUM(sales_amount) AS total_sales,     -- NULL\u3092\u7121\u8996\u3057\u3066\u5408\u7b97\n    AVG(sales_amount) AS avg_sales,       -- NULL\u3092\u9664\u3044\u305f\u4ef6\u6570\u3067\u5272\u308b\n    COUNT(sales_amount) AS sales_count,   -- NULL\u3092\u9664\u3044\u305f\u4ef6\u6570\n    COUNT(*) AS all_count                 -- \u5168\u4ef6\uff08NULL\u542b\u3080\uff09\nFROM monthly_sales;\n-- NULL\u3092\u300c0\u300d\u3068\u898b\u306a\u3057\u305fAVG\u3092\u8a08\u7b97\u3057\u305f\u3044\u5834\u5408\nSELECT AVG(COALESCE(sales_amount, 0)) AS avg_with_zero FROM monthly_sales;<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">5-1. AVG\u306eNULL\u7f60\uff1a\u30bc\u30ed\u3068NULL\u306e\u6df7\u540c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u696d\u52d9\u3067\u6700\u3082\u8aa4\u89e3\u304c\u591a\u3044\u96c6\u8a08\u95a2\u6570\u304cAVG\uff08\u5e73\u5747\uff09\u3067\u3059\u3002AVG\u306fNULL\u3092\u9664\u3044\u305f\u884c\u6570\u3067\u5408\u8a08\u5024\u3092\u5272\u308b\u305f\u3081\u3001\u300c\u58f2\u4e0a\u672a\u767b\u9332\uff08NULL\uff09\uff1d\u58f2\u4e0a\u30bc\u30ed\u300d\u3068\u306f\u7570\u306a\u308b\u610f\u5473\u306b\u306a\u308a\u307e\u3059\u3002\u58f2\u4e0a\u304c5\u4ef6\u3042\u3063\u30663\u4ef6\u306f\u58f2\u4e0a\u91d1\u984d\u304c\u5165\u529b\u6e08\u307f\uff0810\u4e07\u30fb20\u4e07\u30fb30\u4e07\uff09\u30012\u4ef6\u306fNULL\u306e\u5834\u5408\u3001AVG\u306f(10+20+30)\/3 = 20\u4e07\u5186\u3068\u306a\u308a\u307e\u3059\u3002\u3082\u30572\u4ef6\u306eNULL\u3092\u300c0\u5186\u306e\u53d6\u5f15\u300d\u3068\u3057\u3066\u8a08\u7b97\u3057\u305f\u3044\u306a\u3089\u3001COALESCE(sales_amount, 0)\u3067\u30bc\u30ed\u7f6e\u63db\u3057\u3066\u304b\u3089AVG\u3092\u53d6\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u306e\u533a\u5225\u3092\u610f\u8b58\u3057\u3066\u3044\u308b\u304b\u3069\u3046\u304b\u3067\u3001\u96c6\u8a08\u30ec\u30dd\u30fc\u30c8\u306e\u7cbe\u5ea6\u304c\u5909\u308f\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- AVG\u306eNULL vs COALESCE(0)\u306e\u9055\u3044\nSELECT\n    AVG(sales_amount) AS avg_ignore_null,       -- NULL\u3092\u9664\u5916\u3057\u3066\u5e73\u5747\n    AVG(COALESCE(sales_amount, 0)) AS avg_zero  -- NULL\u30920\u3068\u3057\u3066\u5e73\u5747\nFROM sales;\n\n-- \u4f8b: [10\u4e07, 20\u4e07, 30\u4e07, NULL, NULL] \u306e\u5834\u5408\n-- avg_ignore_null = (10+20+30) \/ 3 = 20\u4e07\n-- avg_zero       = (10+20+30+0+0) \/ 5 = 12\u4e07\n-- \u30d3\u30b8\u30cd\u30b9\u8981\u4ef6\u306b\u5408\u308f\u305b\u3066\u3069\u3061\u3089\u3092\u4f7f\u3046\u304b\u5224\u65ad\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b<\/pre>\n<\/div>\n\n\n\n<div style=\"background:#fef2f2;border:2px solid #dc2626;border-radius:8px;padding:20px 24px;margin:24px 0;\">\n  <div style=\"display:flex;align-items:center;gap:8px;margin-bottom:12px;\">\n    <span style=\"font-size:20px;\">&#9888;&#65039;<\/span>\n    <strong style=\"color:#dc2626;font-size:16px;\">\u96c6\u8a08\u30ec\u30dd\u30fc\u30c8\u306eNULL\u7f60\uff1a\u300c\u5c11\u306a\u3044\u300d\u3053\u3068\u306b\u6c17\u3065\u304b\u306a\u3044<\/strong>\n  <\/div>\n  <p style=\"margin:0;font-size:15px;line-height:1.8;color:#333;\">SUM\u30fbAVG\u30fbCOUNT\u304cNULL\u3092\u7121\u8996\u3059\u308b\u3053\u3068\u3067\u3001\u96c6\u8a08\u5024\u304c\u5b9f\u969b\u3088\u308a\u5c11\u306a\u304f\u306a\u308b\u30b1\u30fc\u30b9\u304c\u3042\u308a\u307e\u3059\u3002\u300c\u58f2\u4e0a\u5408\u8a08\u304c\u5148\u6708\u3088\u308a\u5c11\u306a\u3044\u300d\u3068\u601d\u3063\u305f\u3089\u30c7\u30fc\u30bf\u5165\u529b\u6f0f\u308c\uff08NULL\uff09\u304c\u539f\u56e0\u3060\u3063\u305f\u3001\u3068\u3044\u3046\u30d1\u30bf\u30fc\u30f3\u306f\u696d\u52d9\u3067\u3088\u304f\u767a\u751f\u3057\u307e\u3059\u3002\u96c6\u8a08\u30af\u30a8\u30ea\u3092\u66f8\u304f\u969b\u306f\u3001NULL\u304c\u3042\u308b\u3053\u3068\u3092\u524d\u63d0\u306b\u300cNULL\u3092\u3069\u3046\u6271\u3046\u304b\u300d\u3092\u660e\u793a\u7684\u306b\u8a2d\u8a08\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<\/div>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u96c6\u8a08SQL\u306e\u30ec\u30d3\u30e5\u30fc\u3067\u3088\u304f\u898b\u308b\u554f\u984c\u304c\u300cCOUNT(*)\u3067\u4ef6\u6570\u3092\u51fa\u3057\u3066\u3044\u308b\u304c\u5b9f\u306f\u610f\u56f3\u306f\u30e1\u30fc\u30eb\u767b\u9332\u6e08\u307f\u4ef6\u6570\u3060\u3063\u305f\u300d\u3068\u3044\u3046\u30b1\u30fc\u30b9\u3002COUNT(*)\u3068COUNT(email)\u306f\u7d50\u679c\u304c\u9055\u3044\u307e\u3059\u3002\u96c6\u8a08\u95a2\u6570\u306e\u5f15\u6570\u306b\u5217\u540d\u3092\u5165\u308c\u308b\u304b*\u306b\u3059\u308b\u304b\u306f\u3001\u5fc5\u305a\u610f\u56f3\u3092\u6301\u3063\u3066\u9078\u3093\u3067\u304f\u3060\u3055\u3044\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-06\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">06<\/span>\n  <span class=\"section-label\" style=\"display:block;\">CASE EXPRESSION<\/span>\n  <span class=\"section-title\" style=\"display:block;\">CASE\u5f0f\u3067NULL\u3092\u67d4\u8edf\u306b\u5236\u5fa1\u3059\u308b<\/span>\n  <span class=\"section-desc\">NULL\u5224\u5b9a\u30fb\u6761\u4ef6\u5206\u5c90\u30fb\u30e9\u30d9\u30eb\u7f6e\u63db\u3092\u4e00\u6c17\u306b\u5b9f\u73fe\u3059\u308b\u30c6\u30af\u30cb\u30c3\u30af<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">CASE\u5f0f\u306fSQL\u306e\u6761\u4ef6\u5206\u5c90\u69cb\u6587\u3067\u3001NULL\u306e\u6271\u3044\u306b\u3082\u5f37\u529b\u306b\u6d3b\u7528\u3067\u304d\u307e\u3059\u3002IS NULL\u3068CASE\u3092\u7d44\u307f\u5408\u308f\u305b\u308b\u3068\u300cNULL\u306a\u3089\u3007\u3007\u3001\u5024\u304c\u3042\u308c\u3070\u3007\u3007\u3001\u5024\u304c\u25b3\u25b3\u306a\u3089\u3007\u3007\u300d\u3068\u3044\u3046\u8907\u96d1\u306a\u30e9\u30d9\u30eb\u7f6e\u63db\u3084\u5206\u985e\u51e6\u7406\u30921\u3064\u306eSQL\u3067\u5b9f\u73fe\u3067\u304d\u307e\u3059\u3002COALESCE\u95a2\u6570\u3067\u306f\u8868\u73fe\u3067\u304d\u306a\u3044\u300cNULL\u4ee5\u5916\u306e\u5024\u306b\u3082\u6761\u4ef6\u3092\u4ed8\u3051\u305f\u3044\u300d\u30b1\u30fc\u30b9\u3067\u3001CASE\u5f0f\u304c\u5a01\u529b\u3092\u767a\u63ee\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- CASE\u5f0f\u3067NULL\u3092\u30e9\u30d9\u30eb\u5316\u3059\u308b\nSELECT\n    customer_id,\n    customer_name,\n    CASE\n        WHEN email IS NULL THEN &#x27;\u30e1\u30fc\u30eb\u672a\u767b\u9332&#x27;\n        WHEN email LIKE &#x27;%@gmail.com&#x27; THEN &#x27;Gmail&#x27;\n        WHEN email LIKE &#x27;%@yahoo.co.jp&#x27; THEN &#x27;Yahoo&#x27;\n        ELSE &#x27;\u305d\u306e\u4ed6\u306e\u30e1\u30fc\u30eb&#x27;\n    END AS email_category\nFROM customers;\n\n-- NULL\u30fb\u5024\u306e\u5927\u5c0f\u30fb\u7279\u5b9a\u5024\u3092\u7d44\u307f\u5408\u308f\u305b\u305f\u5206\u985e\nSELECT\n    order_id,\n    order_amount,\n    CASE\n        WHEN order_amount IS NULL THEN &#x27;\u91d1\u984d\u672a\u5165\u529b&#x27;\n        WHEN order_amount = 0 THEN &#x27;\u30bc\u30ed\u5186&#x27;\n        WHEN order_amount &lt; 10000 THEN &#x27;\u5c0f\u984d&#x27;\n        WHEN order_amount &lt; 100000 THEN &#x27;\u4e2d\u984d&#x27;\n        ELSE &#x27;\u5927\u53e3&#x27;\n    END AS amount_category\nFROM orders;<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">6-1. NULLIF\u95a2\u6570\uff1a\u7279\u5b9a\u306e\u5024\u3092NULL\u306b\u5909\u63db\u3059\u308b<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">NULLIF(\u50241, \u50242)\u306f\u3001\u50241\u3068\u50242\u304c\u7b49\u3057\u3051\u308c\u3070NULL\u3092\u8fd4\u3057\u3001\u7570\u306a\u308c\u3070\u50241\u3092\u305d\u306e\u307e\u307e\u8fd4\u3059\u95a2\u6570\u3067\u3059\u3002\u30bc\u30ed\u9664\u7b97\u30a8\u30e9\u30fc\u3092\u9632\u3050\u969b\u306b\u3088\u304f\u4f7f\u308f\u308c\u307e\u3059\u3002\u305f\u3068\u3048\u3070\u300c\u58f2\u4e0a\u5408\u8a08 \/ \u4ef6\u6570\u300d\u3092\u8a08\u7b97\u3059\u308b\u3068\u304d\u3001\u4ef6\u6570\u304c0\u306e\u5834\u5408\u306b\u30bc\u30ed\u9664\u7b97\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3057\u307e\u3059\u304c\u3001NULLIF(\u4ef6\u6570, 0)\u3068\u3059\u308b\u3053\u3068\u3067\u4ef6\u6570\u304c0\u306e\u3068\u304d\u306bNULL\u3092\u8fd4\u3057\u3001\u30bc\u30ed\u9664\u7b97\u3092\u56de\u907f\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- NULLIF\u95a2\u6570\uff1a\u30bc\u30ed\u9664\u7b97\u30a8\u30e9\u30fc\u306e\u9632\u6b62\n-- NG\u4f8b: order_count\u304c0\u306e\u3068\u304d\u30bc\u30ed\u9664\u7b97\u30a8\u30e9\u30fc\n-- SELECT total_amount \/ order_count FROM summary;\n\n-- OK\u4f8b: NULLIF\u3067\u30bc\u30ed\u3092NULL\u306b\u5909\u63db\u3057\u3066\u304b\u3089COALESCE\u3067\u6700\u7d42\u7d50\u679c\nSELECT\n    total_amount,\n    order_count,\n    COALESCE(total_amount \/ NULLIF(order_count, 0), 0) AS avg_amount\nFROM\n    monthly_summary;\n\n-- NULLIF\u306e\u3082\u3046\u4e00\u3064\u306e\u4f7f\u3044\u65b9\uff1a\u7279\u5b9a\u306e\u6587\u5b57\u5217\u3092NULL\u306b\u5909\u63db\n-- \u4f8b\uff1a&#x27;N\/A&#x27; \u3084 &#x27;\u306a\u3057&#x27; \u304c\u5165\u3063\u3066\u3044\u308b\u30c7\u30fc\u30bf\u3092NULL\u3068\u3057\u3066\u6271\u3044\u305f\u3044\nSELECT\n    customer_id,\n    NULLIF(company_name, &#x27;N\/A&#x27;) AS company_name,  -- N\/A\u3092NULL\u306b\u5909\u63db\n    NULLIF(remarks, &#x27;&#x27;) AS remarks                  -- \u7a7a\u6587\u5b57\u3092NULL\u306b\u5909\u63db\nFROM customers;<\/pre>\n<\/div>\n\n\n\n<div style=\"background:#f8f9fa;border-left:4px solid #6b7280;border-radius:0 8px 8px 0;padding:16px 20px;margin:20px 0;\">\n  <p style=\"margin:0 0 4px;font-size:13px;font-weight:700;color:#6b7280;letter-spacing:1px;\">&#128218; \u7528\u8a9e\u89e3\u8aac<\/p>\n  <p style=\"margin:0;font-size:15px;line-height:1.7;\"><strong>NULLIF\u95a2\u6570<\/strong>\uff1aNULLIF(\u50241, \u50242)\u306f\u50241\u3068\u50242\u304c\u7b49\u3057\u3044\u3068\u304dNULL\u3092\u8fd4\u3057\u3001\u7570\u306a\u308b\u3068\u304d\u50241\u3092\u8fd4\u3057\u307e\u3059\u3002\u30bc\u30ed\u9664\u7b97\u306e\u9632\u6b62\u306b\u6700\u3082\u3088\u304f\u4f7f\u308f\u308c\u307e\u3059\u3002NULLIF(\u4ef6\u6570, 0)\u3068\u66f8\u304f\u3053\u3068\u3067\u4ef6\u6570\u304c0\u306e\u3068\u304dNULL\u306b\u5909\u63db\u3055\u308c\u3001NULL\u3092\u5206\u6bcd\u306b\u3057\u305f\u9664\u7b97\u306f\u30a8\u30e9\u30fc\u3067\u306f\u306a\u304fNULL\u3092\u8fd4\u3059\u305f\u3081\u5b89\u5168\u3067\u3059\u3002COALESCE\u3068\u7d44\u307f\u5408\u308f\u305b\u3066NULL\u3092\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306b\u7f6e\u63db\u3059\u308b\u30d1\u30bf\u30fc\u30f3\u304c\u5b9a\u77f3\u3067\u3059\u3002<\/p>\n<\/div>\n\n\n\n<div class=\"g-flow-row\" style=\"margin:24px 0;\">\n  <div class=\"g-flow-item\"><strong>NULL\u5224\u5b9a<\/strong><br><span style=\"font-size:12px;\">IS NULL \/<br>IS NOT NULL<\/span><\/div>\n  <div class=\"g-flow-arrow\">&#8594;<\/div>\n  <div class=\"g-flow-item\"><strong>NULL\u7f6e\u63db<\/strong><br><span style=\"font-size:12px;\">COALESCE \/<br>ISNULL \/ NVL<\/span><\/div>\n  <div class=\"g-flow-arrow\">&#8594;<\/div>\n  <div class=\"g-flow-item\"><strong>\u6761\u4ef6\u5206\u5c90<\/strong><br><span style=\"font-size:12px;\">CASE IS NULL<br>THEN...<\/span><\/div>\n  <div class=\"g-flow-arrow\">&#8594;<\/div>\n  <div class=\"g-flow-item\"><strong>\u5024\u2192NULL\u5909\u63db<\/strong><br><span style=\"font-size:12px;\">NULLIF(<br>\u5024, \u5909\u63db\u6761\u4ef6)<\/span><\/div>\n  <div class=\"g-flow-arrow\">&#8594;<\/div>\n  <div class=\"g-flow-item\"><strong>\u96c6\u8a08<\/strong><br><span style=\"font-size:12px;\">COALESCE(AVG(),0)<br>COUNT(*) vs COUNT(\u5217)<\/span><\/div>\n<\/div>\n\n\n\n<div class=\"balloon-wrap\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/ceo-sugasawa.jpg\" alt=\"\u4ee3\u8868\u83c5\u6fa4\">\n    <span class=\"balloon-name\">\u4ee3\u8868\u83c5\u6fa4<\/span>\n  <\/div>\n  <div class=\"balloon-body\">CASE\u5f0f\u306fNULL\u3060\u3051\u3067\u306a\u304f\u696d\u52d9\u30ed\u30b8\u30c3\u30af\u5168\u822c\u306b\u4f7f\u3048\u308b\u5f37\u529b\u306a\u69cb\u6587\u3067\u3059\u3002\u300c\u30b9\u30c6\u30fc\u30bf\u30b9\u30b3\u30fc\u30c9\u3092\u65e5\u672c\u8a9e\u30e9\u30d9\u30eb\u306b\u5909\u63db\u3059\u308b\u300d\u300c\u58f2\u4e0a\u30e9\u30f3\u30af\u3092A\/B\/C\u306b\u5206\u985e\u3059\u308b\u300d\u3068\u3044\u3063\u305f\u51e6\u7406\u3082\u5168\u90e8CASE\u5f0f1\u3064\u3067\u66f8\u3051\u307e\u3059\u3002Claude Code\u306b\u300c\u3053\u306e\u30c7\u30fc\u30bf\u5909\u63db\u30ed\u30b8\u30c3\u30af\u3092SQL\u3067\u66f8\u3044\u3066\u300d\u3068\u8a00\u3046\u3068\u3001CASE\u5f0f\u3092\u4f7f\u3063\u305f\u6700\u9069\u306a\u5f62\u3067\u66f8\u3044\u3066\u304f\u308c\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-07\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">07<\/span>\n  <span class=\"section-label\" style=\"display:block;\">NULL TRAPS<\/span>\n  <span class=\"section-title\" style=\"display:block;\">NULL\u306b\u95a2\u3059\u308b\u3088\u304f\u3042\u308b\u7f60\u3068\u30d0\u30b0\u30d1\u30bf\u30fc\u30f3<\/span>\n  <span class=\"section-desc\">\u696d\u52d9SQL\u3067\u983b\u51fa\u3059\u308bNULL\u8d77\u56e0\u306e\u30d0\u30b0\u3068\u9632\u5fa1\u7684\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">NULL\u306f\u300c\u898b\u3048\u306a\u3044\u30d0\u30b0\u300d\u3092\u751f\u307f\u3084\u3059\u3044\u6982\u5ff5\u3067\u3059\u3002\u30af\u30a8\u30ea\u304c\u6b63\u5e38\u7d42\u4e86\u3057\u3066\u3044\u3066\u3082\u7d50\u679c\u304c\u4e0d\u6b63\u78ba\u3060\u3063\u305f\u308a\u3001\u691c\u7d22\u304c\u610f\u56f3\u901a\u308a\u306b\u6a5f\u80fd\u3057\u3066\u3044\u306a\u304b\u3063\u305f\u308a\u3068\u3044\u3046\u554f\u984c\u304c\u767a\u751f\u3057\u307e\u3059\u3002\u3053\u3053\u3067\u306f\u696d\u52d9SQL\u3067\u983b\u51fa\u3059\u308bNULL\u8d77\u56e0\u306e\u30d0\u30b0\u30d1\u30bf\u30fc\u30f3\u3068\u3001\u305d\u306e\u9632\u5fa1\u7684\u5bfe\u51e6\u6cd5\u3092\u6574\u7406\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">7-1. NOT IN\u3068NULL\uff1a\u5168\u4ef6\u9664\u5916\u306e\u7f60<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u6700\u3082\u5371\u967a\u306aNULL\u30d0\u30b0\u306e1\u3064\u304c\u300cNOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u306bNULL\u304c\u542b\u307e\u308c\u308b\u3068\u5168\u4ef6\u9664\u5916\u3055\u308c\u308b\u300d\u554f\u984c\u3067\u3059\u3002NOT IN\u306f\u5185\u90e8\u7684\u306b\u300c\u5217 <> \u50241 AND \u5217 <> \u50242 AND ...\u300d\u306b\u5c55\u958b\u3055\u308c\u307e\u3059\u304c\u3001\u30b5\u30d6\u30af\u30a8\u30ea\u306e\u4e2d\u306bNULL\u304c1\u4ef6\u3067\u3082\u542b\u307e\u308c\u308b\u3068\u3001\u300c\u5217 <> NULL\u300d\u306e\u6bd4\u8f03\u304cUNKNOWN\u306b\u306a\u308a\u3001\u5168\u884c\u304cWHERE\u6761\u4ef6\u3092\u6e80\u305f\u3055\u306a\u304f\u306a\u3063\u30660\u4ef6\u304c\u8fd4\u308a\u307e\u3059\u3002\u3053\u308c\u306f\u591a\u304f\u306e\u958b\u767a\u8005\u304c\u6700\u521d\u306b\u7d4c\u9a13\u3059\u308b\u91cd\u5927\u306a\u30d0\u30b0\u3067\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- NOT IN\u306bNULL\u304c\u542b\u307e\u308c\u308b\u3068\u5168\u4ef6\u9664\u5916\u3055\u308c\u308b\u7f60\n-- blacklist\u30c6\u30fc\u30d6\u30eb\u306ecustomer_id\u306bNULL\u304c1\u4ef6\u542b\u307e\u308c\u3066\u3044\u308b\u3068\u3059\u308b\n\n-- NG\uff1ablacklist\u306bNULL\u304c\u542b\u307e\u308c\u308b\u30680\u4ef6\u304c\u8fd4\u308b\nSELECT customer_id FROM customers\nWHERE customer_id NOT IN (SELECT customer_id FROM blacklist);\n-- customer_id NOT IN (..., NULL) \u2192 \u5168\u884c\u304cUNKNOWN\u306b\u306a\u308a0\u4ef6\n\n-- OK\u2460\uff1a\u30b5\u30d6\u30af\u30a8\u30ea\u3067NULL\u3092\u9664\u5916\u3057\u3066\u304b\u3089NOT IN\nSELECT customer_id FROM customers\nWHERE customer_id NOT IN (\n    SELECT customer_id FROM blacklist\n    WHERE customer_id IS NOT NULL  -- NULL\u3092\u9664\u5916\uff01\n);\n\n-- OK\u2461\uff1aNOT EXISTS\u306b\u66f8\u304d\u63db\u3048\u308b\uff08NULL\u306e\u5f71\u97ff\u3092\u53d7\u3051\u306a\u3044\uff09\nSELECT c.customer_id FROM customers c\nWHERE NOT EXISTS (\n    SELECT 1 FROM blacklist b\n    WHERE b.customer_id = c.customer_id\n);<\/pre>\n<\/div>\n\n\n\n<div style=\"background:#fef2f2;border:2px solid #dc2626;border-radius:8px;padding:20px 24px;margin:24px 0;\">\n  <div style=\"display:flex;align-items:center;gap:8px;margin-bottom:12px;\">\n    <span style=\"font-size:20px;\">&#9888;&#65039;<\/span>\n    <strong style=\"color:#dc2626;font-size:16px;\">NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u306fNULL\u6df7\u5165\u3067\u5168\u4ef6\u9664\u5916\u306b\u306a\u308b<\/strong>\n  <\/div>\n  <p style=\"margin:0;font-size:15px;line-height:1.8;color:#333;\">NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u3092\u4f7f\u3046\u5834\u5408\u306f\u3001\u30b5\u30d6\u30af\u30a8\u30ea\u306eNULL\u3092\u5fc5\u305aIS NOT NULL\u3067\u9664\u5916\u3059\u308b\u304b\u3001NOT EXISTS\u306b\u66f8\u304d\u63db\u3048\u3066\u304f\u3060\u3055\u3044\u3002\u300cNULL\u304c\u6df7\u5165\u3057\u305f\u3068\u304d\u300d\u3060\u3051\u5168\u4ef6\u304c\u6d88\u3048\u308b\u305f\u3081\u3001\u30c6\u30b9\u30c8\u74b0\u5883\u3067\u306f\u6c17\u3065\u304b\u305a\u672c\u756a\u3067\u554f\u984c\u304c\u767a\u751f\u3059\u308b\u30b1\u30fc\u30b9\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">7-2. NULL\u3092\u542b\u3080\u7b97\u8853\u6f14\u7b97\uff1a\u7d50\u679c\u304c\u5168\u90e8NULL<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">NULL\u3092\u542b\u3080\u7b97\u8853\u6f14\u7b97\uff08\u52a0\u7b97\u30fb\u6e1b\u7b97\u30fb\u4e57\u7b97\u30fb\u9664\u7b97\uff09\u306e\u7d50\u679c\u306f\u5168\u3066NULL\u306b\u306a\u308a\u307e\u3059\u3002\u300c\u6708\u6b21\u58f2\u4e0a + \u524d\u6708\u7e70\u8d8a\u300d\u3092\u8a08\u7b97\u3059\u308b\u3068\u304d\u3001\u3069\u3061\u3089\u304b\u304cNULL\u306a\u3089\u5408\u8a08\u3082NULL\u306b\u306a\u308a\u307e\u3059\u3002\u96c6\u8a08\u30ec\u30dd\u30fc\u30c8\u3067\u300c\u5408\u8a08\u304c\u51fa\u306a\u3044\u300d\u3068\u3044\u3046\u554f\u984c\u306e\u591a\u304f\u306f\u3053\u308c\u304c\u539f\u56e0\u3067\u3059\u3002\u7b97\u8853\u6f14\u7b97\u306e\u524d\u306bCOALESCE\u3067NULL\u30920\u306b\u7f6e\u63db\u3059\u308b\u306e\u304c\u57fa\u672c\u7684\u306a\u5bfe\u51e6\u6cd5\u3067\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- NULL\u3092\u542b\u3080\u7b97\u8853\u6f14\u7b97\u306e\u7f60\nSELECT\n    10 + NULL,   -- \u2192 NULL\uff0810\u3067\u306f\u306a\u3044\uff09\n    NULL * 5,    -- \u2192 NULL\uff080\u3067\u306f\u306a\u3044\uff09\n    NULL \/ 2,    -- \u2192 NULL\n    NULL + NULL  -- \u2192 NULL\n\n-- \u5b9f\u52d9\u3067\u306e\u9632\u5fa1\u7684\u8a08\u7b97\nSELECT\n    order_id,\n    COALESCE(base_amount, 0) + COALESCE(tax_amount, 0) AS total_amount\nFROM orders;\n-- \u3069\u3061\u3089\u304b\u304cNULL\u3067\u30820\u3068\u3057\u3066\u8a08\u7b97\u3055\u308c\u308b<\/pre>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">7-3. JOIN\u306eNULL\uff1a\u7d50\u5408\u30ad\u30fc\u304cNULL\u306e\u884c\u306f\u5fc5\u305a\u9664\u5916<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">INNER JOIN\u3067\u3082LEFT JOIN\u3067\u3082\u3001\u7d50\u5408\u30ad\u30fc\uff08ON\u53e5\u306e\u6761\u4ef6\uff09\u304cNULL\u306e\u884c\u306f\u300c\u4e00\u81f4\u306a\u3057\u300d\u3068\u3057\u3066\u6271\u308f\u308c\u307e\u3059\u3002\u9867\u5ba2\u30c6\u30fc\u30d6\u30eb\u306ecustomer_id\u304cNULL\u306e\u884c\u306f\u3001\u6ce8\u6587\u30c6\u30fc\u30d6\u30eb\u3068JOIN\u3057\u3066\u3082\u7d50\u5408\u3055\u308c\u307e\u305b\u3093\u3002\u300cLEFT JOIN\u306a\u306e\u306b\u7d50\u679c\u304c\u5c11\u306a\u3044\u300d\u3068\u611f\u3058\u308b\u30b1\u30fc\u30b9\u306e\u539f\u56e0\u3068\u3057\u3066\u3001\u7d50\u5408\u30ad\u30fc\u306eNULL\u304c\u6319\u3052\u3089\u308c\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#1e1e1e;border-radius:8px;padding:20px 24px;margin:20px 0;overflow-x:auto;\">\n  <pre style=\"margin:0;font-family:'Courier New',monospace;font-size:13px;line-height:1.8;color:#d4d4d4;white-space:pre-wrap;\">-- JOIN\u3068NULL\u306e\u6319\u52d5\u78ba\u8a8d\n-- NULL = NULL\u306fFALSE\u3067\u306f\u306a\u304fUNKNOWN\u306e\u305f\u3081\u3001\n-- NULL\u306e\u30ad\u30fc\u540c\u58eb\u306f\u7d50\u5408\u3055\u308c\u306a\u3044\n\nSELECT\n    c.customer_id,\n    c.customer_name,\n    o.order_id\nFROM\n    customers c\n    LEFT JOIN orders o ON c.customer_id = o.customer_id\nWHERE\n    c.customer_id IS NOT NULL;  -- NULL\u30ad\u30fc\u3092\u660e\u793a\u7684\u306b\u9664\u5916\u3059\u308b\u9632\u5fa1\u7b56\n\n-- NULL\u30ad\u30fc\u306e\u5b58\u5728\u78ba\u8a8d\nSELECT COUNT(*) AS null_key_count\nFROM customers\nWHERE customer_id IS NULL;<\/pre>\n<\/div>\n\n\n\n<div style=\"background:#fafafa;border-radius:8px;padding:16px 20px;margin:16px 0;border-left:4px solid #dc2626;\">\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\uff1a\u30b5\u30d6\u30af\u30a8\u30ea\u306eNULL\u3092IS NOT NULL\u3067\u5fc5\u305a\u9664\u5916\u3059\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u7b97\u8853\u6f14\u7b97\uff1aCOALESCE(\u5217, 0)\u3067NULL\u3092\u30bc\u30ed\u306b\u7f6e\u63db\u3057\u3066\u304b\u3089\u8a08\u7b97<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>JOIN\u7d50\u5408\u30ad\u30fc\uff1aNULL\u30ad\u30fc\u304c\u542b\u307e\u308c\u308b\u3068\u7d50\u5408\u3055\u308c\u306a\u3044\uff08\u4e8b\u524d\u306bIS NOT NULL\u3067\u78ba\u8a8d\uff09<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>WHERE\u6761\u4ef6\uff1aNULL\u3092\u9664\u5916\u3057\u305f\u3044\u5834\u5408\u306fIS NOT NULL\u3092\u660e\u793a\u7684\u306b\u66f8\u304f<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>ORDER BY\uff1aNULL\u306e\u4e26\u3073\u9806\u306fDBMS\u306b\u3088\u3063\u3066\u7570\u306a\u308b\uff08NULLS FIRST\/LAST \u3067\u5236\u5fa1\uff09<\/span><\/div>\n\n<\/div>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">NOT IN\u306bNULL\u304c\u6df7\u5165\u3059\u308b\u30d0\u30b0\u306f\u3001\u30c6\u30b9\u30c8\u30c7\u30fc\u30bf\u306bNULL\u304c\u306a\u3044\u5834\u5408\u306f\u6c17\u3065\u304b\u305a\u306b\u672c\u756a\u3067\u521d\u3081\u3066\u554f\u984c\u304c\u767a\u899a\u3059\u308b\u30b1\u30fc\u30b9\u304c\u591a\u3044\u3067\u3059\u3002NOT IN\u3092\u4f7f\u3046\u969b\u306f\u5fc5\u305aIS NOT NULL\u3092\u30b5\u30d6\u30af\u30a8\u30ea\u306b\u5165\u308c\u308b\u3001\u307e\u305f\u306fNOT EXISTS\u306b\u66f8\u304d\u63db\u3048\u308b\u3053\u3068\u3092\u30eb\u30fc\u30eb\u5316\u3059\u308b\u3053\u3068\u3092\u304a\u52e7\u3081\u3057\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-08\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">08<\/span>\n  <span class=\"section-label\" style=\"display:block;\">CLAUDE CODE<\/span>\n  <span class=\"section-title\" style=\"display:block;\">Claude Code\u3067SQL\u30af\u30a8\u30ea\u3092\u81ea\u52d5\u751f\u6210\u3059\u308b<\/span>\n  <span class=\"section-desc\">NULL\u3092\u8003\u616e\u3057\u305f\u5805\u7262\u306aSQL\u3092AI\u306b\u751f\u6210\u3055\u305b\u308b\u5b9f\u8df5\u30ac\u30a4\u30c9<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u3053\u307e\u3067NULL\u306b\u95a2\u3059\u308b\u69d8\u3005\u306a\u77e5\u8b58\u3092\u89e3\u8aac\u3057\u3066\u304d\u307e\u3057\u305f\u3002\u3053\u308c\u3089\u3092\u6bce\u56de\u6b63\u78ba\u306b\u5b9f\u88c5\u3059\u308b\u306e\u306f\u3001\u7279\u306bSQL\u306b\u6163\u308c\u3066\u3044\u306a\u3044\u975e\u30a8\u30f3\u30b8\u30cb\u30a2\u306e\u65b9\u306b\u306f\u5927\u5909\u3067\u3059\u3002\u5f0a\u793e\uff08\u682a\u5f0f\u4f1a\u793eGENAI\uff09\u3067\u306f\u3001Claude Code\u3078\u306eSQL\u81ea\u52d5\u751f\u6210\u3092\u6d3b\u7528\u3059\u308b\u3053\u3068\u3067\u3001NULL\u51e6\u7406\u3092\u542b\u3080\u8907\u96d1\u306a\u96c6\u8a08\u30af\u30a8\u30ea\u3092\u6b63\u78ba\u304b\u3064\u9ad8\u901f\u306b\u751f\u6210\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Claude Code\u306b\u306f\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u95a2\u9023\u306e\u5e45\u5e83\u3044\u77e5\u8b58\u304c\u7d44\u307f\u8fbc\u307e\u308c\u3066\u304a\u308a\u3001\u300c\u3069\u306eDBMS\u3092\u4f7f\u3063\u3066\u3044\u308b\u304b\u300d\u300cNULL\u3092\u3069\u3046\u6271\u3044\u305f\u3044\u304b\u300d\u3092\u8aac\u660e\u3059\u308b\u3060\u3051\u3067\u3001COALESCE\u30fbIS NULL\u30fbCASE\u5f0f\u3092\u7d44\u307f\u5408\u308f\u305b\u305f\u5805\u7262\u306aSQL\u3092\u751f\u6210\u3057\u3066\u304f\u308c\u307e\u3059\u3002SQL\u8a2d\u8a08\u306e\u7d4c\u9a13\u304c\u6d45\u3044\u30e1\u30f3\u30d0\u30fc\u3067\u3082\u3001AI\u304c\u751f\u6210\u3057\u305fSQL\u3092\u8aad\u307f\u89e3\u304f\u3053\u3068\u3067\u5b9f\u529b\u304c\u8eab\u306b\u3064\u304f\u52b9\u679c\u3082\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"balloon-wrap\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/ceo-sugasawa.jpg\" alt=\"\u4ee3\u8868\u83c5\u6fa4\">\n    <span class=\"balloon-name\">\u4ee3\u8868\u83c5\u6fa4<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u5f0a\u793e\u3067\u306f\u6bce\u6708\u306e\u58f2\u4e0a\u5206\u6790\u30fb\u9867\u5ba2\u30d5\u30a3\u30eb\u30bf\u30ea\u30f3\u30b0\u30fb\u30c7\u30fc\u30bf\u54c1\u8cea\u30c1\u30a7\u30c3\u30af\u306eSQL\u3092\u307b\u307c\u5168\u3066Claude Code\u3067\u751f\u6210\u3057\u3066\u3044\u307e\u3059\u3002\u300cNULL\u30920\u3068\u3057\u3066\u6271\u3063\u3066\u90e8\u9580\u5225\u306e\u5e73\u5747\u58f2\u4e0a\u3092\u51fa\u3057\u305f\u3044\u300d\u3068\u4f1d\u3048\u308b\u3068\u3001COALESCE + AVG\u306e\u7d44\u307f\u5408\u308f\u305b\u3092\u6b63\u78ba\u306b\u66f8\u3044\u3066\u304f\u308c\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n\n<div style=\"background:#fafafa;border-radius:8px;padding:16px 20px;margin:16px 0;border-left:4px solid #dc2626;\">\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u4f7f\u3063\u3066\u3044\u308bDBMS\uff08SQL Server\u30fbMySQL\u30fbOracle\u30fbPostgreSQL\uff09\u3092\u4f1d\u3048\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u300cNULL\u3092\u30bc\u30ed\u3068\u3057\u3066\u6271\u3046\u300d\u300cNULL\u3092\u9664\u5916\u3057\u3066\u96c6\u8a08\u3059\u308b\u300d\u306a\u3069\u3001NULL\u306e\u6271\u3044\u65b9\u3092\u660e\u793a\u3059\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u300cNOT IN\u3067\u306f\u306a\u304fNOT EXISTS\u3067\u66f8\u3044\u3066\u300d\u306a\u3069\u3001\u30d0\u30b0\u3092\u907f\u3051\u305f\u3044\u5834\u5408\u306f\u65b9\u91dd\u3092\u6307\u793a\u3059\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u751f\u6210\u3055\u308c\u305fSQL\u306e\u30b3\u30e1\u30f3\u30c8\u3092\u8aad\u3093\u3067\u3001NULL\u3078\u306e\u914d\u616e\u304c\u3069\u3053\u306b\u5165\u3063\u3066\u3044\u308b\u304b\u78ba\u8a8d\u3059\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u300c\u3053\u306eSQL\u306bNULL\u51e6\u7406\u306e\u554f\u984c\u70b9\u304c\u3042\u308c\u3070\u6559\u3048\u3066\u300d\u3068\u30ec\u30d3\u30e5\u30fc\u3092\u4f9d\u983c\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u308b<\/span><\/div>\n\n<\/div>\n\n\n\n<div style=\"background:#f0fdf4;border:1px solid #22c55e;border-radius:8px;padding:20px 24px;margin:24px 0;\">\n  <div style=\"display:flex;align-items:center;gap:8px;margin-bottom:12px;\">\n    <span style=\"font-size:18px;\">&#128161;<\/span>\n    <strong style=\"color:#16a34a;font-size:15px;\">Claude Code\u3078\u306eSQL\u4f9d\u983c\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8<\/strong>\n  <\/div>\n  <p style=\"margin:0;font-size:15px;line-height:1.8;color:#333;\">\u300cMySQL\u3092\u4f7f\u3063\u3066\u3044\u307e\u3059\u3002orders\u30c6\u30fc\u30d6\u30eb\uff08order_id, customer_id, amount, status\uff09\u304b\u3089\u3001status\u304cNULL\u304b\"\u30ad\u30e3\u30f3\u30bb\u30eb\"\u306e\u6ce8\u6587\u3092\u9664\u5916\u3057\u3066\u3001customer_id\u3054\u3068\u306bamount\u3092\u5408\u8a08\u3059\u308bSQL\u3092\u66f8\u3044\u3066\u304f\u3060\u3055\u3044\u3002amount\u304cNULL\u306e\u5834\u5408\u306f0\u3068\u3057\u3066\u5408\u8a08\u306b\u542b\u3081\u3066\u304f\u3060\u3055\u3044\u3002\u300d\u3053\u306e\u3088\u3046\u306b\u3001DBMS\u30fb\u5bfe\u8c61\u30c6\u30fc\u30d6\u30eb\u30fbNULL\u306e\u6271\u3044\u65b9\u3092\u542b\u3081\u3066\u4f1d\u3048\u308b\u3068\u3001\u6b63\u78ba\u306aSQL\u304c\u751f\u6210\u3055\u308c\u307e\u3059\u3002<\/p>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Claude Code\u3092\u4f7f\u3063\u305fSQL\u81ea\u52d5\u751f\u6210\u306e\u3082\u3046\u4e00\u3064\u306e\u30e1\u30ea\u30c3\u30c8\u306f\u300cSQL\u30ec\u30d3\u30e5\u30fc\u6a5f\u80fd\u300d\u3067\u3059\u3002\u65e2\u5b58\u306eSQL\u3092\u8cbc\u308a\u4ed8\u3051\u3066\u300cNULL\u306e\u6271\u3044\u306b\u554f\u984c\u304c\u306a\u3044\u304b\u78ba\u8a8d\u3057\u3066\u300d\u3068\u4f9d\u983c\u3059\u308b\u3068\u3001NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u306eNULL\u554f\u984c\u3084\u3001AVG\u306e\u30bc\u30ed\u7f6e\u63db\u6f0f\u308c\u306a\u3069\u3001\u6f5c\u5728\u7684\u306a\u30d0\u30b0\u3092\u6307\u6458\u3057\u3066\u304f\u308c\u307e\u3059\u3002\u696d\u52d9\u30af\u30ea\u30c6\u30a3\u30ab\u30eb\u306a\u96c6\u8a08SQL\u306e\u54c1\u8cea\u5411\u4e0a\u306b\u6d3b\u7528\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u5f0a\u793e\u306e\u30c7\u30fc\u30bf\u30a2\u30ca\u30ea\u30b9\u30c8\u304c\u66f8\u3044\u305fSQL\u3092Claude Code\u306b\u30ec\u30d3\u30e5\u30fc\u3055\u305b\u305f\u3068\u3053\u308d\u3001NOT IN\u306eNULL\u554f\u984c\u3092\u542b\u3080\u6f5c\u5728\u30d0\u30b0\u304c3\u4ef6\u767a\u898b\u3055\u308c\u307e\u3057\u305f\u3002\u672c\u756a\u30c7\u30fc\u30bf\u3067\u306f\u554f\u984c\u306a\u304f\u52d5\u3044\u3066\u3044\u307e\u3057\u305f\u304c\u3001\u30c7\u30fc\u30bf\u304c\u5897\u3048\u3066NULL\u304c\u6df7\u5165\u3057\u305f\u77ac\u9593\u306b\u554f\u984c\u304c\u9855\u5728\u5316\u3057\u3066\u3044\u305f\u3067\u3057\u3087\u3046\u3002\u5b9a\u671f\u7684\u306aSQL\u30ec\u30d3\u30e5\u30fc\u306b\u3082AI\u3092\u6d3b\u7528\u3059\u308b\u3053\u3068\u3092\u304a\u52e7\u3081\u3057\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n<div style=\"margin:48px 0 8px;display:flex;gap:12px;justify-content:center;flex-wrap:wrap;\"><a href=\"https:\/\/aikanri.genai-ai.co.jp\/seminar2-blog\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_content=cc-sql-null-guide&#038;blog_slug=cc-sql-null-guide\" target=\"_blank\" rel=\"noopener\" aria-label=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff08\u7121\u6599\u30fb1on1\u30fb60\u5206\uff09\u306e\u4e88\u7d04\u753b\u9762\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_seminar_claude_code_2026.jpg\" alt=\"Claude Code \u5b8c\u5168\u89e3\u8aac\u30bb\u30df\u30ca\u30fc\uff5c\u7d4c\u55b6\u8005\u30fb\u4f1a\u793e\u5f79\u54e1\u5c02\u7528 1on1 60\u5206 \u7121\u6599\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&#038;utm_medium=h2banner&#038;utm_campaign=cc-sql-null-guide&#038;utm_content=h2-banner-kanri\" target=\"_blank\" rel=\"noopener\" aria-label=\"AI\u9b3c\u7ba1\u7406 \u516c\u5f0f\u30b5\u30a4\u30c8\u3078\" style=\"flex:1 1 280px;max-width:360px;text-decoration:none;\"><img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/05\/cta_blog_1to1.jpg\" alt=\"Claude Code\u3092\u7d4c\u55b6\u306b\u6d3b\u304b\u3057\u305f\u3044\u65b9\u3078 \u2014 AI\u9b3c\u7ba1\u7406\" style=\"width:100%;height:auto;border-radius:8px;display:block;\"><\/a><\/div>\n\n\n<div id=\"sec-09\"><\/div>\n<h2 class=\"section-header-img\" style=\"margin:32px 0 24px;border-radius:8px;overflow:hidden;background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);padding:32px 28px;color:#fff;position:relative;border:none;border-left:none;text-align:left;\">\n  <span class=\"section-number\" style=\"display:block;\">09<\/span>\n  <span class=\"section-label\" style=\"display:block;\">CONCLUSION<\/span>\n  <span class=\"section-title\" style=\"display:block;\">\u307e\u3068\u3081<\/span>\n  <span class=\"section-desc\">SQL\u306eNULL\u51e6\u7406\u3092\u5b8c\u5168\u306b\u30de\u30b9\u30bf\u30fc\u3059\u308b\u305f\u3081\u306e\u30dd\u30a4\u30f3\u30c8\u6574\u7406<\/span>\n<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001SQL\u306eNULL\u5024\u306e\u6271\u3044\u65b9\u30928\u3064\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u4f53\u7cfb\u7684\u306b\u89e3\u8aac\u3057\u307e\u3057\u305f\u3002NULL\u51e6\u7406\u306fSQL\u306e\u4e2d\u3067\u3082\u300c\u77e5\u3089\u306a\u3044\u3068\u9759\u304b\u306b\u30d0\u30b0\u304c\u51fa\u308b\u300d\u9818\u57df\u3067\u3042\u308a\u3001\u4e00\u5ea6\u6b63\u78ba\u306b\u7406\u89e3\u3059\u308b\u3053\u3068\u3067\u696d\u52d9\u30af\u30a8\u30ea\u306e\u54c1\u8cea\u304c\u5927\u5e45\u306b\u5411\u4e0a\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<div style=\"background:#fafafa;border-radius:8px;padding:16px 20px;margin:16px 0;border-left:4px solid #dc2626;\">\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NULL\u306f0\u30fb\u7a7a\u6587\u5b57\u3068\u306f\u5225\u7269\u3002\u300c\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u300d\u3053\u3068\u3092\u8868\u3059\u7279\u6b8a\u306a\u30de\u30fc\u30ab\u30fc<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>\u300c= NULL\u300d\u306fNG\u3002NULL\u5224\u5b9a\u306b\u306f\u5fc5\u305aIS NULL\u30fbIS NOT NULL\u3092\u4f7f\u3046\uff08\u4e09\u5024\u8ad6\u7406\u306e\u4ed5\u7d44\u307f\uff09<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NULL\u7f6e\u63db\u306fCOALESCE\u63a8\u5968\uff08\u5168DB\u5bfe\u5fdc\uff09\u3002SQL Server=ISNULL\u3001Oracle=NVL\u3001MySQL=IFNULL<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>COUNT(*)\u306f\u5168\u884c\u3001COUNT(\u5217\u540d)\u306fNULL\u3092\u9664\u3044\u305f\u4ef6\u6570\u3002\u96c6\u8a08\u306e\u610f\u56f3\u306b\u5408\u308f\u305b\u3066\u4f7f\u3044\u5206\u3051\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>AVG\u306fNULL\u3092\u7121\u8996\u3057\u3066\u5272\u308b\u3002\u30bc\u30ed\u3068\u3057\u3066\u6271\u3044\u305f\u3044\u306a\u3089COALESCE(\u5217, 0)\u3067\u7f6e\u63db\u3057\u3066\u304b\u3089AVG<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u306bNULL\u304c\u6df7\u5165\u3059\u308b\u3068\u5168\u4ef6\u9664\u5916\u3002IS NOT NULL\u9664\u5916\u307e\u305f\u306fNOT EXISTS\u306b\u66f8\u304d\u63db\u3048\u308b<\/span><\/div>\n<div style=\"display:flex;align-items:flex-start;gap:8px;padding:6px 0;font-size:15px;line-height:1.6;\"><span style=\"color:#dc2626;font-size:16px;flex-shrink:0;margin-top:2px;\">&#10004;&#65039;<\/span><span>NULLIF\u95a2\u6570\u3067\u30bc\u30ed\u9664\u7b97\u3092\u9632\u6b62\u3002NULL\u3092\u542b\u3080\u7b97\u8853\u6f14\u7b97\u306f\u5168\u3066NULL\u306b\u306a\u308b\u3053\u3068\u3092\u610f\u8b58\u3059\u308b<\/span><\/div>\n\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">NULL\u3092\u6b63\u78ba\u306b\u6271\u3048\u308bSQL\u306f\u3001\u30c7\u30fc\u30bf\u54c1\u8cea\u3068\u5206\u6790\u7cbe\u5ea6\u306b\u76f4\u7d50\u3057\u307e\u3059\u3002\u300c\u306a\u305c\u304b\u30c7\u30fc\u30bf\u304c\u5c11\u306a\u3044\u300d\u300c\u96c6\u8a08\u5024\u304c\u671f\u5f85\u3068\u9055\u3046\u300d\u3068\u3044\u3046\u554f\u984c\u306e\u591a\u304f\u306fNULL\u306e\u8aa4\u3063\u305f\u53d6\u308a\u6271\u3044\u304c\u539f\u56e0\u3067\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3067\u7d39\u4ecb\u3057\u305f\u30d1\u30bf\u30fc\u30f3\u3092\u5b9f\u52d9\u306b\u53d6\u308a\u5165\u308c\u308b\u3053\u3068\u3067\u3001\u3053\u3046\u3057\u305f\u554f\u984c\u3092\u4e8b\u524d\u306b\u9632\u3052\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u307e\u305f\u3001Claude Code\u3092\u6d3b\u7528\u3059\u308b\u3053\u3068\u3067\u3001NULL\u3092\u8003\u616e\u3057\u305f\u5805\u7262\u306aSQL\u3092\u81ea\u52d5\u751f\u6210\u30fb\u30ec\u30d3\u30e5\u30fc\u3067\u304d\u307e\u3059\u3002\u5f0a\u793e\uff08\u682a\u5f0f\u4f1a\u793eGENAI\uff09\u3067\u306f\u3001\u30c7\u30fc\u30bf\u6d3b\u7528\u30fb\u696d\u52d9\u81ea\u52d5\u5316\u306e\u8a2d\u8a08\u652f\u63f4\u3092\u300cAI\u9b3c\u7ba1\u7406\u300d\u3068\u3057\u3066\u63d0\u4f9b\u3057\u3066\u3044\u307e\u3059\u3002SQL\u8a2d\u8a08\u3084\u30c7\u30fc\u30bf\u54c1\u8cea\u306e\u6539\u5584\u306b\u3064\u3044\u3066\u3082\u3001\u7121\u6599\u76f8\u8ac7\u3067\u3054\u76f8\u8ac7\u3044\u305f\u3060\u3051\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"balloon-wrap\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/ceo-sugasawa.jpg\" alt=\"\u4ee3\u8868\u83c5\u6fa4\">\n    <span class=\"balloon-name\">\u4ee3\u8868\u83c5\u6fa4<\/span>\n  <\/div>\n  <div class=\"balloon-body\">NULL\u306e\u77e5\u8b58\u306f\u300c\u77e5\u3063\u3066\u308b\u3060\u3051\u3067\u5b9f\u52d9\u306e\u7cbe\u5ea6\u304c\u5909\u308f\u308b\u300d\u4ee3\u8868\u7684\u306a\u9818\u57df\u3067\u3059\u3002\u4eca\u65e5\u5b66\u3093\u3060IS NULL\u30fbCOALESCE\u30fbNOT EXISTS\u306e\u30d1\u30bf\u30fc\u30f3\u3092\u3001\u6b21\u306b\u66f8\u304fSQL\u304b\u3089\u610f\u8b58\u7684\u306b\u4f7f\u3063\u3066\u307f\u3066\u304f\u3060\u3055\u3044\u3002<\/div>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">SQL\u3068\u30c7\u30fc\u30bf\u6d3b\u7528\u306e\u81ea\u52d5\u5316\u3092\u3001AI\u9b3c\u7ba1\u7406\u304c\u4e00\u7dd2\u306b\u8a2d\u8a08\u3057\u307e\u3059<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u300c\u696d\u52d9\u30c7\u30fc\u30bf\u306e\u96c6\u8a08\u3084\u5206\u6790\u3092SQL\u3067\u81ea\u52d5\u5316\u3057\u305f\u3044\u300d\u300c\u65e2\u5b58\u306eSQL\u306bNULL\u51e6\u7406\u306e\u4e0d\u5099\u304c\u306a\u3044\u304b\u78ba\u8a8d\u3057\u305f\u3044\u300d\u3068\u3044\u3046\u65b9\u306b\u5411\u3051\u3066\u3001\u5f0a\u793e\u3067\u306fClaude Code\u3092\u6d3b\u7528\u3057\u305f\u30c7\u30fc\u30bf\u6d3b\u7528\u30fbSQL\u8a2d\u8a08\u306e\u652f\u63f4\u3092\u884c\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"balloon-wrap is-right\">\n  <div class=\"balloon-icon\">\n    <img decoding=\"async\" src=\"https:\/\/genai-ai.co.jp\/ai-kanri\/wp-content\/uploads\/2026\/04\/yamazaki-avatar.png\" alt=\"AI\u9b3c\u7ba1\u7406\u5c71\u5d0e\">\n    <span class=\"balloon-name\">AI\u9b3c\u7ba1\u7406\u5c71\u5d0e<\/span>\n  <\/div>\n  <div class=\"balloon-body\">\u300cSQL\u306f\u4f55\u3068\u306a\u304f\u66f8\u3051\u308b\u304c\u3001NULL\u3084\u8907\u96d1\u306a\u7d50\u5408\u306b\u81ea\u4fe1\u304c\u306a\u3044\u300d\u3068\u3044\u3046\u65b9\u3082\u6b53\u8fce\u3067\u3059\u3002\u307e\u305a\u306f\u7121\u6599\u76f8\u8ac7\u3067\u73fe\u72b6\u306e\u8ab2\u984c\u3092\u304a\u805e\u304b\u305b\u304f\u3060\u3055\u3044\u3002\u6700\u77ed\u3067\u6210\u679c\u304c\u51fa\u308b\u30c7\u30fc\u30bf\u6d3b\u7528\u306e\u4ed5\u7d44\u307f\u3092\u3054\u63d0\u6848\u3057\u307e\u3059\u3002<\/div>\n<\/div>\n\n\n\n<div style=\"background:linear-gradient(135deg,#1a1a1a 0%,#2a1015 100%);border-radius:16px;padding:36px 32px;margin:48px 0 16px;color:#fff;\">\n  <p style=\"font-size:13px;font-weight:700;color:#dc2626;letter-spacing:2px;margin:0 0 12px;\">NEXT STEP<\/p>\n  <p style=\"font-size:22px;font-weight:800;line-height:1.5;margin:0 0 20px;\">\u3053\u306e\u8a18\u4e8b\u306e\u5185\u5bb9\u3092\u3001\u3042\u306a\u305f\u306e\u30d3\u30b8\u30cd\u30b9\u3067<br>\u5b9f\u8df5\u3057\u3066\u307f\u307e\u305b\u3093\u304b\uff1f<\/p>\n  <div style=\"background:rgba(255,255,255,0.06);border:1px solid rgba(255,255,255,0.12);border-radius:12px;padding:24px;max-width:560px;margin:0 auto;\">\n    <p style=\"font-size:13px;color:#dc2626;font-weight:700;margin:0 0 8px;\">AI\u6d3b\u7528\u3092\u81ea\u793e\u3067\u56de\u305b\u308b\u3088\u3046\u306b\u306a\u308a\u305f\u3044\u65b9\u3078<\/p>\n    <p style=\"font-size:20px;font-weight:800;margin:0 0 12px;\">AI\u9b3c\u7ba1\u7406<\/p>\n    <p style=\"font-size:14px;color:rgba(255,255,255,0.75);margin:0 0 20px;line-height:1.7;\">Claude Code\u30fbCowork\u5c0e\u5165\u652f\u63f4\u304b\u3089\u696d\u52d9\u8a2d\u8a08\u30fb\u793e\u5185\u6d78\u900f\u307e\u3067\u5b9f\u8df5\u30d9\u30fc\u30b9\u3067\u4f34\u8d70\u3002\u300c\u81ea\u793e\u3067\u56de\u305b\u308b\u7d44\u7e54\u300d\u309290\u65e5\u3067\u4f5c\u308b\u7d4c\u55b6\u8005\u5411\u3051\u30c8\u30ec\u30fc\u30cb\u30f3\u30b0\u3002<\/p>\n    <div style=\"text-align:center;\">\n      <a href=\"https:\/\/aikanri.genai-ai.co.jp\/?utm_source=blog&utm_medium=article&utm_campaign=cc-sql-null-guide&utm_content=next-step-cta\" target=\"_blank\" rel=\"noopener\" style=\"display:inline-block;background:#dc2626;color:#fff;font-weight:700;font-size:15px;padding:14px 32px;border-radius:30px;text-decoration:none;\">AI\u9b3c\u7ba1\u7406\u3092\u8a73\u3057\u304f\u898b\u308b \u2192<\/a>\n    <\/div>\n  <\/div>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"faq\">\u3088\u304f\u3042\u308b\u8cea\u554f<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Q. SQL\u3067\u300c= NULL\u300d\u3068\u66f8\u304f\u3068\u306a\u305c\u52d5\u304b\u306a\u3044\u306e\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. SQL\u306f\u4e09\u5024\u8ad6\u7406\uff08TRUE\u30fbFALSE\u30fbUNKNOWN\uff09\u3092\u63a1\u7528\u3057\u3066\u304a\u308a\u3001NULL\u3092\u542b\u3080\u6bd4\u8f03\u6f14\u7b97\u306f\u5e38\u306bUNKNOWN\u3092\u8fd4\u3057\u307e\u3059\u3002WHERE\u53e5\u3067UNKNOWN\u306b\u306a\u3063\u305f\u884c\u306f\u7d50\u679c\u304b\u3089\u9664\u5916\u3055\u308c\u308b\u305f\u3081\u3001\u300c= NULL\u300d\u306f\u5e38\u306b0\u4ef6\u304c\u8fd4\u308a\u307e\u3059\u3002NULL\u3092\u691c\u7d22\u3059\u308b\u306b\u306f\u5c02\u7528\u306eIS NULL\u6f14\u7b97\u5b50\u3092\u4f7f\u3063\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q. COALESCE\u3068ISNULL\u306f\u3069\u3061\u3089\u3092\u4f7f\u3048\u3070\u3044\u3044\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. COALESCE\u63a8\u5968\u3067\u3059\u3002COALESCE(\u5217, \u4ee3\u66ff\u5024)\u306fSQL\u6a19\u6e96\u3067\u5168\u3066\u306eDBMS\uff08SQL Server\u30fbMySQL\u30fbOracle\u30fbPostgreSQL\uff09\u3067\u52d5\u304d\u307e\u3059\u3002ISNULL\u306fSQL Server\u5c02\u7528\u95a2\u6570\u306e\u305f\u3081\u3001DB\u3092\u79fb\u884c\u3059\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u5834\u5408\u3084\u8907\u6570\u74b0\u5883\u306b\u5bfe\u5fdc\u3057\u305fSQL\u3092\u66f8\u304f\u5834\u5408\u306fCOALESCE\u306b\u7d71\u4e00\u3059\u308b\u306e\u304c\u5b89\u5168\u3067\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q. COUNT(*)\u3068COUNT(\u5217\u540d)\u306e\u9055\u3044\u306f\u4f55\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. COUNT(*)\u306fNULL\u3092\u542b\u3080\u5168\u884c\u3092\u6570\u3048\u307e\u3059\u3002COUNT(\u5217\u540d)\u306f\u305d\u306e\u5217\u304cNULL\u3067\u306a\u3044\u884c\u3060\u3051\u3092\u6570\u3048\u307e\u3059\u3002\u4f8b\u3048\u307010\u884c\u3042\u3063\u3066email\u304c3\u884cNULL\u306e\u5834\u5408\u3001COUNT(*) = 10\u3001COUNT(email) = 7 \u306b\u306a\u308a\u307e\u3059\u3002\u96c6\u8a08\u306e\u610f\u56f3\uff08\u5168\u4ef6\u6570 vs \u5165\u529b\u6e08\u307f\u4ef6\u6570\uff09\u306b\u5408\u308f\u305b\u3066\u4f7f\u3044\u5206\u3051\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q. NULL\u306e\u30c7\u30fc\u30bf\u3092JOIN\u3057\u3066\u3082\u7d50\u5408\u3055\u308c\u306a\u3044\u306e\u306f\u306a\u305c\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. ON\u53e5\u306e\u7d50\u5408\u6761\u4ef6\u3067NULL\u304c\u95a2\u4e0e\u3059\u308b\u6bd4\u8f03\u306f\u4e09\u5024\u8ad6\u7406\u306b\u3088\u308aUNKNOWN\u306b\u306a\u308b\u305f\u3081\u3001\u7d50\u5408\u6761\u4ef6\u304c\u6210\u7acb\u3057\u307e\u305b\u3093\u3002\u3064\u307e\u308a\u7d50\u5408\u30ad\u30fc\u304cNULL\u306e\u884c\u306f\u3001INNER JOIN\u306f\u3082\u3061\u308d\u3093\u3001LEFT JOIN\u3067\u3082\u7d50\u5408\u76f8\u624b\u3092\u898b\u3064\u3051\u3089\u308c\u307e\u305b\u3093\u3002NULL\u306e\u30ad\u30fc\u304c\u542b\u307e\u308c\u308b\u30c7\u30fc\u30bf\u3092JOIN\u3059\u308b\u5834\u5408\u306f\u3001\u4e8b\u524d\u306bIS NOT NULL\u3067NULL\u3092\u9664\u5916\u3059\u308b\u304b\u3001COALESCE(key, -1)\u306e\u3088\u3046\u306bNULL\u4ee5\u5916\u306e\u5024\u306b\u5909\u63db\u3059\u308b\u8a2d\u8a08\u304c\u5fc5\u8981\u3067\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q. NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u3092\u4f7f\u3046\u3068\u5168\u4ef6\u9664\u5916\u3055\u308c\u308b\u3053\u3068\u304c\u3042\u308b\u306e\u306f\u306a\u305c\u3067\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. NOT IN\u306f\u30b5\u30d6\u30af\u30a8\u30ea\u306e\u5168\u5024\u3068\u300c<> \u6bd4\u8f03\u300d\u3092\u884c\u3044\u307e\u3059\u3002\u30b5\u30d6\u30af\u30a8\u30ea\u306e\u7d50\u679c\u306bNULL\u304c1\u4ef6\u3067\u3082\u542b\u307e\u308c\u308b\u3068\u300c\u5217 <> NULL\u300d\u306e\u8a55\u4fa1\u304cUNKNOWN\u306b\u306a\u308a\u3001\u5168\u3066\u306e\u884c\u304cWHERE\u6761\u4ef6\u3092\u6e80\u305f\u3055\u306a\u304f\u306a\u308a\u307e\u3059\u3002\u5bfe\u7b56\u306f\u2460\u30b5\u30d6\u30af\u30a8\u30ea\u306bWHERE \u5217 IS NOT NULL\u3092\u8ffd\u52a0\u3059\u308b\u3001\u2461NOT EXISTS\u306b\u66f8\u304d\u63db\u3048\u308b\u3001\u306e\u3069\u3061\u3089\u304b\u3067\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q. AVG\u3092\u8a08\u7b97\u3059\u308b\u3068NULL\u304c\u542b\u307e\u308c\u308b\u884c\u306f\u7121\u8996\u3055\u308c\u307e\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. \u306f\u3044\u3001AVG\u306fNULL\u3092\u9664\u3044\u305f\u884c\u306e\u307f\u3067\u8a08\u7b97\u3057\u307e\u3059\u30025\u884c\u3042\u3063\u30662\u884c\u304cNULL\u306e\u5834\u5408\u3001\u6b8b\u308a3\u884c\u306e\u5024\u306e\u5408\u8a08\u30923\u3067\u5272\u3063\u305f\u5024\u304c\u8fd4\u308a\u307e\u3059\u3002NULL\u3092\u300c0\u3068\u3057\u3066\u8a08\u7b97\u3057\u305f\u5e73\u5747\u300d\u3092\u6c42\u3081\u305f\u3044\u5834\u5408\u306f\u3001AVG(COALESCE(\u5217\u540d, 0))\u3068\u66f8\u3044\u3066\u304f\u3060\u3055\u3044\u3002\u3069\u3061\u3089\u306e\u610f\u5473\u3067\u5e73\u5747\u3092\u51fa\u3057\u305f\u3044\u304b\u306f\u30d3\u30b8\u30cd\u30b9\u8981\u4ef6\u306b\u3088\u3063\u3066\u7570\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q. SQL\u306eNULL\u51e6\u7406\u304c\u8907\u96d1\u3059\u304e\u3066\u81ea\u5206\u3067\u66f8\u3051\u306a\u3044\u306e\u3067\u3059\u304c\u3001AI\u3067\u81ea\u52d5\u751f\u6210\u3067\u304d\u307e\u3059\u304b\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. \u3067\u304d\u307e\u3059\u3002Claude Code\u306b\u5bfe\u3057\u3066\u300cMySQL\u3067\u4f7f\u3063\u3066\u3044\u307e\u3059\u3002NULL\u3092\u30bc\u30ed\u3068\u3057\u3066\u96c6\u8a08\u3057\u305f\u3044\u300d\u306a\u3069DBMS\u3068\u8981\u4ef6\u3092\u4f1d\u3048\u308b\u3068\u3001COALESCE\u30fbIS NOT NULL\u30fbCASE\u5f0f\u3092\u7d44\u307f\u5408\u308f\u305b\u305fNULL\u51e6\u7406\u6e08\u307f\u306eSQL\u3092\u751f\u6210\u3057\u3066\u304f\u308c\u307e\u3059\u3002\u307e\u305f\u65e2\u5b58\u306eSQL\u3092\u8cbc\u308a\u4ed8\u3051\u3066\u300cNULL\u51e6\u7406\u306b\u554f\u984c\u304c\u306a\u3044\u304b\u78ba\u8a8d\u3057\u3066\u300d\u3068\u30ec\u30d3\u30e5\u30fc\u3092\u4f9d\u983c\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [\n    {\n      \"@type\": \"Question\",\n      \"name\": \"SQL\u3067\u300c= NULL\u300d\u3068\u66f8\u304f\u3068\u306a\u305c\u52d5\u304b\u306a\u3044\u306e\u3067\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"SQL\u306f\u4e09\u5024\u8ad6\u7406\uff08TRUE\u30fbFALSE\u30fbUNKNOWN\uff09\u3092\u63a1\u7528\u3057\u3066\u304a\u308a\u3001NULL\u3092\u542b\u3080\u6bd4\u8f03\u6f14\u7b97\u306f\u5e38\u306bUNKNOWN\u3092\u8fd4\u3057\u307e\u3059\u3002WHERE\u53e5\u3067UNKNOWN\u306b\u306a\u3063\u305f\u884c\u306f\u7d50\u679c\u304b\u3089\u9664\u5916\u3055\u308c\u308b\u305f\u3081\u3001\u300c= NULL\u300d\u306f\u5e38\u306b0\u4ef6\u304c\u8fd4\u308a\u307e\u3059\u3002NULL\u3092\u691c\u7d22\u3059\u308b\u306b\u306f\u5c02\u7528\u306eIS NULL\u6f14\u7b97\u5b50\u3092\u4f7f\u3063\u3066\u304f\u3060\u3055\u3044\u3002\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"COALESCE\u3068ISNULL\u306f\u3069\u3061\u3089\u3092\u4f7f\u3048\u3070\u3044\u3044\u3067\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"COALESCE\u63a8\u5968\u3067\u3059\u3002COALESCE(\u5217, \u4ee3\u66ff\u5024)\u306fSQL\u6a19\u6e96\u3067\u5168\u3066\u306eDBMS\uff08SQL Server\u30fbMySQL\u30fbOracle\u30fbPostgreSQL\uff09\u3067\u52d5\u304d\u307e\u3059\u3002ISNULL\u306fSQL Server\u5c02\u7528\u95a2\u6570\u306e\u305f\u3081\u3001DB\u3092\u79fb\u884c\u3059\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u5834\u5408\u3084\u8907\u6570\u74b0\u5883\u306b\u5bfe\u5fdc\u3057\u305fSQL\u3092\u66f8\u304f\u5834\u5408\u306fCOALESCE\u306b\u7d71\u4e00\u3059\u308b\u306e\u304c\u5b89\u5168\u3067\u3059\u3002\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"COUNT(*)\u3068COUNT(\u5217\u540d)\u306e\u9055\u3044\u306f\u4f55\u3067\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"COUNT(*)\u306fNULL\u3092\u542b\u3080\u5168\u884c\u3092\u6570\u3048\u307e\u3059\u3002COUNT(\u5217\u540d)\u306f\u305d\u306e\u5217\u304cNULL\u3067\u306a\u3044\u884c\u3060\u3051\u3092\u6570\u3048\u307e\u3059\u3002\u4f8b\u3048\u307010\u884c\u3042\u3063\u3066email\u304c3\u884cNULL\u306e\u5834\u5408\u3001COUNT(*) = 10\u3001COUNT(email) = 7 \u306b\u306a\u308a\u307e\u3059\u3002\u96c6\u8a08\u306e\u610f\u56f3\uff08\u5168\u4ef6\u6570 vs \u5165\u529b\u6e08\u307f\u4ef6\u6570\uff09\u306b\u5408\u308f\u305b\u3066\u4f7f\u3044\u5206\u3051\u3066\u304f\u3060\u3055\u3044\u3002\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"NULL\u306e\u30c7\u30fc\u30bf\u3092JOIN\u3057\u3066\u3082\u7d50\u5408\u3055\u308c\u306a\u3044\u306e\u306f\u306a\u305c\u3067\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"ON\u53e5\u306e\u7d50\u5408\u6761\u4ef6\u3067NULL\u304c\u95a2\u4e0e\u3059\u308b\u6bd4\u8f03\u306f\u4e09\u5024\u8ad6\u7406\u306b\u3088\u308aUNKNOWN\u306b\u306a\u308b\u305f\u3081\u3001\u7d50\u5408\u6761\u4ef6\u304c\u6210\u7acb\u3057\u307e\u305b\u3093\u3002\u3064\u307e\u308a\u7d50\u5408\u30ad\u30fc\u304cNULL\u306e\u884c\u306f\u3001INNER JOIN\u306f\u3082\u3061\u308d\u3093\u3001LEFT JOIN\u3067\u3082\u7d50\u5408\u76f8\u624b\u3092\u898b\u3064\u3051\u3089\u308c\u307e\u305b\u3093\u3002NULL\u306e\u30ad\u30fc\u304c\u542b\u307e\u308c\u308b\u30c7\u30fc\u30bf\u3092JOIN\u3059\u308b\u5834\u5408\u306f\u3001\u4e8b\u524d\u306bIS NOT NULL\u3067NULL\u3092\u9664\u5916\u3059\u308b\u304b\u3001COALESCE(key, -1)\u306e\u3088\u3046\u306bNULL\u4ee5\u5916\u306e\u5024\u306b\u5909\u63db\u3059\u308b\u8a2d\u8a08\u304c\u5fc5\u8981\u3067\u3059\u3002\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"NOT IN\uff08\u30b5\u30d6\u30af\u30a8\u30ea\uff09\u3092\u4f7f\u3046\u3068\u5168\u4ef6\u9664\u5916\u3055\u308c\u308b\u3053\u3068\u304c\u3042\u308b\u306e\u306f\u306a\u305c\u3067\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"NOT IN\u306f\u30b5\u30d6\u30af\u30a8\u30ea\u306e\u5168\u5024\u3068\u300c<> \u6bd4\u8f03\u300d\u3092\u884c\u3044\u307e\u3059\u3002\u30b5\u30d6\u30af\u30a8\u30ea\u306e\u7d50\u679c\u306bNULL\u304c1\u4ef6\u3067\u3082\u542b\u307e\u308c\u308b\u3068\u300c\u5217 <> NULL\u300d\u306e\u8a55\u4fa1\u304cUNKNOWN\u306b\u306a\u308a\u3001\u5168\u3066\u306e\u884c\u304cWHERE\u6761\u4ef6\u3092\u6e80\u305f\u3055\u306a\u304f\u306a\u308a\u307e\u3059\u3002\u5bfe\u7b56\u306f\u2460\u30b5\u30d6\u30af\u30a8\u30ea\u306bWHERE \u5217 IS NOT NULL\u3092\u8ffd\u52a0\u3059\u308b\u3001\u2461NOT EXISTS\u306b\u66f8\u304d\u63db\u3048\u308b\u3001\u306e\u3069\u3061\u3089\u304b\u3067\u3059\u3002\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"AVG\u3092\u8a08\u7b97\u3059\u308b\u3068NULL\u304c\u542b\u307e\u308c\u308b\u884c\u306f\u7121\u8996\u3055\u308c\u307e\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"\u306f\u3044\u3001AVG\u306fNULL\u3092\u9664\u3044\u305f\u884c\u306e\u307f\u3067\u8a08\u7b97\u3057\u307e\u3059\u30025\u884c\u3042\u3063\u30662\u884c\u304cNULL\u306e\u5834\u5408\u3001\u6b8b\u308a3\u884c\u306e\u5024\u306e\u5408\u8a08\u30923\u3067\u5272\u3063\u305f\u5024\u304c\u8fd4\u308a\u307e\u3059\u3002NULL\u3092\u300c0\u3068\u3057\u3066\u8a08\u7b97\u3057\u305f\u5e73\u5747\u300d\u3092\u6c42\u3081\u305f\u3044\u5834\u5408\u306f\u3001AVG(COALESCE(\u5217\u540d, 0))\u3068\u66f8\u3044\u3066\u304f\u3060\u3055\u3044\u3002\u3069\u3061\u3089\u306e\u610f\u5473\u3067\u5e73\u5747\u3092\u51fa\u3057\u305f\u3044\u304b\u306f\u30d3\u30b8\u30cd\u30b9\u8981\u4ef6\u306b\u3088\u3063\u3066\u7570\u306a\u308a\u307e\u3059\u3002\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"SQL\u306eNULL\u51e6\u7406\u304c\u8907\u96d1\u3059\u304e\u3066\u81ea\u5206\u3067\u66f8\u3051\u306a\u3044\u306e\u3067\u3059\u304c\u3001AI\u3067\u81ea\u52d5\u751f\u6210\u3067\u304d\u307e\u3059\u304b\uff1f\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"\u3067\u304d\u307e\u3059\u3002Claude Code\u306b\u5bfe\u3057\u3066\u300cMySQL\u3067\u4f7f\u3063\u3066\u3044\u307e\u3059\u3002NULL\u3092\u30bc\u30ed\u3068\u3057\u3066\u96c6\u8a08\u3057\u305f\u3044\u300d\u306a\u3069DBMS\u3068\u8981\u4ef6\u3092\u4f1d\u3048\u308b\u3068\u3001COALESCE\u30fbIS NOT NULL\u30fbCASE\u5f0f\u3092\u7d44\u307f\u5408\u308f\u305b\u305fNULL\u51e6\u7406\u6e08\u307f\u306eSQL\u3092\u751f\u6210\u3057\u3066\u304f\u308c\u307e\u3059\u3002\u307e\u305f\u65e2\u5b58\u306eSQL\u3092\u8cbc\u308a\u4ed8\u3051\u3066\u300cNULL\u51e6\u7406\u306b\u554f\u984c\u304c\u306a\u3044\u304b\u78ba\u8a8d\u3057\u3066\u300d\u3068\u30ec\u30d3\u30e5\u30fc\u3092\u4f9d\u983c\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002\"\n      }\n    }\n  ]\n}\n<\/script>\n\n\n","protected":false},"excerpt":{"rendered":"<p>SQL\u306eNULL\u5024\u306e\u6271\u3044\u65b9\u3092\u5b8c\u5168\u89e3\u8aac\u3002IS NULL\/IS NOT 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