{"id":199661,"date":"2025-05-06T09:12:21","date_gmt":"2025-05-06T01:12:21","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199661\/"},"modified":"2025-05-06T09:12:21","modified_gmt":"2025-05-06T01:12:21","slug":"%e4%bd%bf%e7%94%a8sql%e4%b8%ad%e7%9a%84%e6%9d%a1%e4%bb%b6%e5%87%bd%e6%95%b0if","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199661\/","title":{"rendered":"\u4f7f\u7528SQL\u4e2d\u7684\u6761\u4ef6\u51fd\u6570IF"},"content":{"rendered":"

<\/b> <\/p>\n

\u4f7f\u7528SQL\u4e2d\u7684\u6761\u4ef6\u51fd\u6570IF<\/h1>\n

\u7f16\u7a0b\u5e76\u4e0d\u662f\u4e00\u4e2a\u673a\u68b0\u6027\u7684\u5de5\u4f5c\uff0c\u800c\u662f\u9700\u8981\u6709\u601d\u8003\uff0c\u6709\u521b\u65b0\u7684\u5de5\u4f5c\uff0c\u8bed\u6cd5\u662f\u56fa\u5b9a\u7684\uff0c\u4f46\u89e3\u51b3\u95ee\u9898\u7684\u601d\u8def\u5219\u662f\u4f9d\u9760\u4eba\u7684\u601d\u7ef4\uff0c\u8fd9\u5c31\u9700\u8981\u6211\u4eec\u575a\u6301\u5b66\u4e60\u548c\u66f4\u65b0\u81ea\u5df1\u7684\u77e5\u8bc6\u3002\u4eca\u5929\u4e3b\u673a\u5b9d\u8d1d\u5c31\u6574\u7406\u5206\u4eab\u300a\u4f7f\u7528SQL\u4e2d\u7684\u6761\u4ef6\u51fd\u6570IF\u300b\uff0c\u6587\u7ae0\u8bb2\u89e3\u7684\u77e5\u8bc6\u70b9\u4e3b\u8981\u5305\u62ec\uff0c\u5982\u679c\u4f60\u5bf9\u6570\u636e\u5e93\u65b9\u9762\u7684\u77e5\u8bc6\u70b9\u611f\u5174\u8da3\uff0c\u5c31\u4e0d\u8981\u9519\u8fc7\u4e3b\u673a\u5b9d\u8d1d\uff0c\u5728\u8fd9\u53ef\u4ee5\u5bf9\u5927\u5bb6\u7684\u77e5\u8bc6\u79ef\u7d2f\u6709\u6240\u5e2e\u52a9\uff0c\u52a9\u529b\u5f00\u53d1\u80fd\u529b\u7684\u63d0\u5347\u3002<\/p>\n

SQL\u4e2dIF\u51fd\u6570\u7684\u7528\u6cd5\u53ca\u4ee3\u7801\u793a\u4f8b<\/p>\n

SQL\u8bed\u8a00\u4e2d\u7684IF\u51fd\u6570\u662f\u4e00\u79cd\u6761\u4ef6\u5224\u65ad\u51fd\u6570\uff0c\u7528\u4e8e\u6839\u636e\u6761\u4ef6\u7684\u771f\u5047\u8fd4\u56de\u4e0d\u540c\u7684\u7ed3\u679c\u3002\u5b83\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u5b9e\u73b0\u4e00\u4e9b\u590d\u6742\u7684\u903b\u8f91\u5224\u65ad\u548c\u6570\u636e\u5904\u7406\u64cd\u4f5c\u3002\u4e0b\u9762\u6211\u4eec\u5c06\u8be6\u7ec6\u4ecb\u7ecdIF\u51fd\u6570\u7684\u8bed\u6cd5\u548c\u7528\u6cd5\uff0c\u5e76\u63d0\u4f9b\u4e00\u4e9b\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\u3002<\/p>\n

IF\u51fd\u6570\u7684\u57fa\u672c\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n

IF(condition, value_if_true, value_if_false)<\/pre>\n
\u5176\u4e2d\uff0ccondition\u4e3a\u5f85\u5224\u65ad\u7684\u6761\u4ef6\u8868\u8fbe\u5f0f\uff0cvalue_if_true\u4e3a\u6761\u4ef6\u4e3a\u771f\u65f6\u7684\u8fd4\u56de\u503c\uff0cvalue_if_false\u4e3a\u6761\u4ef6\u4e3a\u5047\u65f6\u7684\u8fd4\u56de\u503c\u3002\u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u901a\u8fc7\u4e00\u4e9b\u5b9e\u9645\u7684\u4f8b\u5b50\u6765\u8bf4\u660eIF\u51fd\u6570\u7684\u5177\u4f53\u7528\u6cd5\u3002<\/p>\n
\u4f8b1\uff1a\u6839\u636e\u5b66\u751f\u6210\u7ee9\u5224\u65ad\u662f\u5426\u53ca\u683c
\u5047\u8bbe\u6709\u4e00\u4e2a\u5b66\u751f\u6210\u7ee9\u8868”Student”\uff0c\u5305\u542b\u5b57\u6bb5”Name”\u548c”Score”\uff0c\u6211\u4eec\u60f3\u8981\u6839\u636e\u5b66\u751f\u7684\u5206\u6570\u5224\u65ad\u4ed6\u4eec\u662f\u5426\u53ca\u683c\u3002\u82e5\u6210\u7ee9\u5927\u4e8e\u7b49\u4e8e60\u5206\uff0c\u5219\u6807\u8bb0\u4e3a\u201c\u53ca\u683c\u201d\uff0c\u5426\u5219\u6807\u8bb0\u4e3a\u201c\u4e0d\u53ca\u683c\u201d\u3002<\/p>\n
SELECT Name, Score, \n   IF(Score >= 60, '\u53ca\u683c', '\u4e0d\u53ca\u683c') AS Grade\nFROM Student;<\/pre>\n
\u4f8b2\uff1a\u6839\u636e\u8ba2\u5355\u91d1\u989d\u8ba1\u7b97\u6298\u6263\u4ef7\u683c
\u5047\u8bbe\u6709\u4e00\u4e2a\u8ba2\u5355\u8868”Orders”\uff0c\u5305\u542b\u5b57\u6bb5”Order_ID”\u548c”Amount”\uff0c\u6211\u4eec\u8981\u6839\u636e\u8ba2\u5355\u91d1\u989d\u8ba1\u7b97\u6298\u6263\u4ef7\u683c\u3002\u82e5\u8ba2\u5355\u91d1\u989d\u5927\u4e8e\u7b49\u4e8e500\uff0c\u5219\u6309\u71678\u6298\u8ba1\u7b97\uff1b\u5426\u5219\u6309\u71679\u6298\u8ba1\u7b97\u3002<\/p>\n
SELECT Order_ID, Amount, \n   IF(Amount >= 500, Amount * 0.8, Amount * 0.9) AS DiscountedPrice\nFROM Orders;<\/pre>\n
\u4f8b3\uff1a\u6839\u636e\u8ba2\u5355\u72b6\u6001\u5224\u65ad\u64cd\u4f5c\u6743\u9650
\u5047\u8bbe\u6709\u4e00\u4e2a\u8ba2\u5355\u8868”Orders”\uff0c\u5305\u542b\u5b57\u6bb5”Order_ID”\u548c”Status”\uff0c\u6211\u4eec\u60f3\u8981\u6839\u636e\u8ba2\u5355\u7684\u72b6\u6001\u5224\u65ad\u7528\u6237\u7684\u64cd\u4f5c\u6743\u9650\u3002\u5982\u679c\u8ba2\u5355\u72b6\u6001\u4e3a”\u5df2\u4ed8\u6b3e”\u6216”\u5df2\u53d1\u8d27”\uff0c\u5219\u5141\u8bb8\u7528\u6237\u8fdb\u884c\u9000\u8d27\u64cd\u4f5c\uff1b\u5426\u5219\u4e0d\u5141\u8bb8\u3002<\/p>\n
SELECT Order_ID, Status, \n   IF(Status = '\u5df2\u4ed8\u6b3e' OR Status = '\u5df2\u53d1\u8d27', '\u5141\u8bb8\u9000\u8d27', '\u4e0d\u5141\u8bb8\u9000\u8d27') AS Permission\nFROM Orders;<\/pre>\n
\u901a\u8fc7\u4ee5\u4e0a\u7684\u4f8b\u5b50\uff0c\u6211\u4eec\u53ef\u4ee5\u770b\u5230IF\u51fd\u6570\u5728SQL\u4e2d\u7684\u7075\u6d3b\u8fd0\u7528\u3002\u5b83\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u6839\u636e\u6761\u4ef6\u7684\u771f\u5047\u6765\u8fd4\u56de\u4e0d\u540c\u7684\u7ed3\u679c\uff0c\u4ece\u800c\u5b9e\u73b0\u590d\u6742\u7684\u903b\u8f91\u5224\u65ad\u548c\u6570\u636e\u5904\u7406\u64cd\u4f5c\u3002\u540c\u65f6\uff0cIF\u51fd\u6570\u4e5f\u53ef\u4ee5\u4e0e\u5176\u4ed6\u51fd\u6570\u548c\u64cd\u4f5c\u7b26\u4e00\u8d77\u4f7f\u7528\uff0c\u4ee5\u6ee1\u8db3\u66f4\u591a\u5b9e\u9645\u5e94\u7528\u7684\u9700\u6c42\u3002<\/p>\n
\u603b\u7ed3\uff1a
IF\u51fd\u6570\u662fSQL\u4e2d\u7684\u4e00\u79cd\u6761\u4ef6\u5224\u65ad\u51fd\u6570\uff0c\u7528\u4e8e\u6839\u636e\u6761\u4ef6\u7684\u771f\u5047\u8fd4\u56de\u4e0d\u540c\u7684\u7ed3\u679c\u3002\u5176\u8bed\u6cd5\u4e3aIF(condition, value_if_true, value_if_false)\u3002\u901a\u8fc7IF\u51fd\u6570\uff0c\u6211\u4eec\u53ef\u4ee5\u5b9e\u73b0\u590d\u6742\u7684\u903b\u8f91\u5224\u65ad\u548c\u6570\u636e\u5904\u7406\u64cd\u4f5c\u3002\u5728\u4f7f\u7528IF\u51fd\u6570\u65f6\uff0c\u9700\u8981\u6839\u636e\u5177\u4f53\u7684\u9700\u6c42\u548c\u8868\u8fbe\u5f0f\u8bed\u6cd5\u6765\u7f16\u5199\u4ee3\u7801\u3002<\/p>\n
\u4ee5\u4e0a\u662f\u5173\u4e8eSQL\u4e2dIF\u51fd\u6570\u7684\u7528\u6cd5\u53ca\u4ee3\u7801\u793a\u4f8b\u7684\u4ecb\u7ecd\uff0c\u5e0c\u671b\u80fd\u5bf9\u8bfb\u8005\u5728\u4f7f\u7528IF\u51fd\u6570\u65f6\u63d0\u4f9b\u4e00\u4e9b\u5e2e\u52a9\u548c\u53c2\u8003\u3002<\/p>\n
\u5230\u8fd9\u91cc\uff0c\u6211\u4eec\u4e5f\u5c31\u8bb2\u5b8c\u4e86\u300a\u4f7f\u7528SQL\u4e2d\u7684\u6761\u4ef6\u51fd\u6570IF\u300b\u7684\u5185\u5bb9\u4e86\u3002\u4e2a\u4eba\u8ba4\u4e3a\uff0c\u57fa\u7840\u77e5\u8bc6\u7684\u5b66\u4e60\u548c\u5de9\u56fa\uff0c\u662f\u4e3a\u4e86\u66f4\u597d\u7684\u5c06\u5176\u8fd0\u7528\u5230\u9879\u76ee\u4e2d\uff0c\u6b22\u8fce\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff0c\u5e26\u4f60\u4e86\u89e3\u66f4\u591a\u5173\u4e8e\u7684\u77e5\u8bc6\u70b9\uff01<\/p>\n
\n
\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"
\u4f7f\u7528SQL\u4e2d\u7684\u6761\u4ef6\u51fd\u6570IF \u7f16\u7a0b...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-199661","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199661","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=199661"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199661\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199661"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199661"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199661"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}