{"id":5970,"date":"2024-11-14T13:04:42","date_gmt":"2024-11-14T05:04:42","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5970\/"},"modified":"2024-11-14T13:04:42","modified_gmt":"2024-11-14T05:04:42","slug":"sql-if%e8%af%ad%e5%8f%a5%e6%80%8e%e4%b9%88%e7%94%a8","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5970\/","title":{"rendered":"sql\u00a0if\u8bed\u53e5\u600e\u4e48\u7528"},"content":{"rendered":"

\n sql if \u8bed\u53e5\u7528\u4e8e\u6709\u6761\u4ef6\u5730\u6267\u884c sql \u8bed\u53e5\uff0c\u8bed\u6cd5\u4e3a\uff1a if (condition) then {\u8bed\u53e5} else {\u8bed\u53e5} end if;\u3002\u6761\u4ef6\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 sql \u8868\u8fbe\u5f0f\uff0c\u5982\u679c\u6761\u4ef6\u4e3a\u771f\uff0c\u6267\u884c then \u5b50\u53e5\uff1b\u5982\u679c\u6761\u4ef6\u4e3a\u5047\uff0c\u6267\u884c else \u5b50\u53e5\u3002if \u8bed\u53e5\u53ef\u4ee5\u5d4c\u5957\uff0c\u5141\u8bb8\u66f4\u590d\u6742\u7684\u6761\u4ef6\u68c0\u67e5\u3002\n<\/p><\/blockquote>\n

\"sql\u00a0if\u8bed\u53e5\u600e\u4e48\u7528\u63d2\u56fe\"<\/p>\n

SQL IF \u8bed\u53e5\u7528\u6cd5<\/strong><\/p>\n

SQL IF \u8bed\u53e5\u7528\u4e8e\u6709\u6761\u4ef6\u5730\u6267\u884c SQL \u8bed\u53e5\u3002\u5b83\u5141\u8bb8\u60a8\u6839\u636e\u7279\u5b9a\u6761\u4ef6\u6267\u884c\u6216\u4e0d\u6267\u884c\u4ee3\u7801\u5757\u3002<\/p>\n

\u8bed\u6cd5<\/strong><\/p>\n

IF (condition) THEN\n  -- \u6761\u4ef6\u4e3a\u771f\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5\nELSE\n  -- \u6761\u4ef6\u4e3a\u5047\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5\nEND IF;<\/pre>\n
  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
\u7528\u6cd5<\/strong><\/p>\n
    \n
  1. \n
    \u6307\u5b9a\u6761\u4ef6\uff1a<\/strong>\u5728 IF \u8bed\u53e5\u4e2d\uff0c\u60a8\u9700\u8981\u6307\u5b9a\u4e00\u4e2a\u6761\u4ef6\uff0c\u4ee5\u51b3\u5b9a\u662f\u5426\u6267\u884c\u8be5\u8bed\u53e5\u5757\u3002\u6761\u4ef6\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 SQL \u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a<\/p>\n
      \n
    • column_name = value<\/li>\n
    • column_name > value<\/li>\n
    • column_name IS NULL<\/li>\n<\/ul>\n<\/li>\n
    • \n
      \u6267\u884c\u8bed\u53e5\uff1a<\/strong>\u5982\u679c\u6761\u4ef6\u4e3a\u771f\uff0c\u5219\u6267\u884c THEN \u5b50\u53e5\u4e2d\u7684\u8bed\u53e5\u3002\u5982\u679c\u6761\u4ef6\u4e3a\u5047\uff0c\u5219\u6267\u884c ELSE \u5b50\u53e5\u4e2d\u7684\u8bed\u53e5\u3002\u8bed\u53e5\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 SQL \u8bed\u53e5\uff0c\u4f8b\u5982\uff1a<\/p>\n
        \n
      • \u63d2\u5165\u6570\u636e<\/li>\n
      • \u66f4\u65b0\u6570\u636e<\/li>\n
      • \u5220\u9664\u6570\u636e<\/li>\n<\/ul>\n<\/li>\n
      •  \u5d4c\u5957 IF \u8bed\u53e5\uff1a<\/strong>\u60a8\u53ef\u4ee5\u5c06 IF \u8bed\u53e5\u5d4c\u5957\u5728\u5176\u4ed6 IF \u8bed\u53e5\u4e2d\uff0c\u4ee5\u521b\u5efa\u66f4\u590d\u6742\u7684\u6761\u4ef6\u68c0\u67e5\u3002\u4f8b\u5982\uff1a<\/li>\n<\/ol>\n
        IF (condition1) THEN\n  -- \u6761\u4ef6 1 \u4e3a\u771f\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5\n  IF (condition2) THEN\n    -- \u6761\u4ef6 2 \u4e3a\u771f\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5\n  ELSE\n    -- \u6761\u4ef6 2 \u4e3a\u5047\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5\n  END IF;\nELSE\n  -- \u6761\u4ef6 1 \u4e3a\u5047\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5\nEND IF;<\/pre>\n
          \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
        \u793a\u4f8b<\/strong><\/p>\n
        \u4ee5\u4e0b\u793a\u4f8b\u6f14\u793a\u4e86 SQL IF \u8bed\u53e5\u7684\u7528\u6cd5\uff1a<\/p>\n
        -- \u68c0\u67e5 customers \u8868\u4e2d\u5ba2\u6237\u7684\u5e74\u9f84\uff0c\u5982\u679c\u5927\u4e8e 18 \u5c81\uff0c\u5219\u6388\u4e88\u4ed6\u4eec\u8bbf\u95ee\u6743\u9650\n\nIF (age > 18) THEN\n  UPDATE customers SET access_level = 'granted';\nELSE\n  UPDATE customers SET access_level = 'denied';\nEND IF;<\/pre>\n
          \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
        \u4ee5\u4e0a\u5c31\u662fsql if\u8bed\u53e5\u600e\u4e48\u7528\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
        sql if \u8bed\u53e5\u7528\u4e8e\u6709\u6761\u4ef6\u5730\u6267\u884c sql \u8bed\u53e5\uff0c\u8bed\u6cd5\u4e3a\uff1a if (condition) then {\u8bed\u53e5} else {\u8bed\u53e5} end if;\u3002\u6761\u4ef6\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 sql \u8868\u8fbe\u5f0f\uff0c\u5982\u679c\u6761\u4ef6\u4e3a\u771f\uff0c\u6267\u884c then \u5b50\u53e5\uff1b\u5982\u679c\u6761\u4ef6\u4e3a\u5047\uff0c\u6267\u884c else \u5b50\u53e5\u3002if \u8bed\u53e5\u53ef\u4ee5\u5d4c\u5957\uff0c\u5141\u8bb8\u66f4\u590d\u6742\u7684\u6761\u4ef6\u68c0\u67e5\u3002 SQL IF \u8bed\u53e5\u7528\u6cd5 SQL IF \u8bed\u53e5\u7528\u4e8e\u6709\u6761\u4ef6\u5730\u6267\u884c SQL \u8bed\u53e5\u3002\u5b83\u5141\u8bb8\u60a8\u6839\u636e\u7279\u5b9a\u6761\u4ef6\u6267\u884c\u6216\u4e0d\u6267\u884c\u4ee3\u7801\u5757\u3002 \u8bed\u6cd5 IF (condition) THEN — \u6761\u4ef6\u4e3a\u771f\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5 ELSE — \u6761\u4ef6\u4e3a\u5047\u65f6\u8981\u6267\u884c\u7684\u8bed\u53e5 END IF; \u767b\u5f55\u540e\u590d\u5236 \u7528\u6cd5 \u6307\u5b9a\u6761\u4ef6\uff1a\u5728 IF \u8bed\u53e5\u4e2d\uff0c\u60a8\u9700\u8981\u6307\u5b9a\u4e00\u4e2a\u6761\u4ef6\uff0c\u4ee5\u51b3\u5b9a\u662f\u5426\u6267\u884c\u8be5\u8bed\u53e5\u5757\u3002\u6761\u4ef6\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 SQL \u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a column_name = value column_name > value column_name IS NULL […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-5970","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5970","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=5970"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5970\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5970"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5970"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5970"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}