{"id":188406,"date":"2024-11-11T22:26:23","date_gmt":"2024-11-11T14:26:23","guid":{"rendered":"https:\/\/server.hk\/cnblog\/188406\/"},"modified":"2024-11-11T22:26:24","modified_gmt":"2024-11-11T14:26:24","slug":"%e6%8e%a2%e7%a9%b6sql%e4%b8%adcase%e8%aa%9e%e5%8f%a5%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/188406\/","title":{"rendered":"\u63a2\u7a76SQL\u4e2dCase\u8a9e\u53e5\u7528\u6cd5"},"content":{"rendered":"<h1 id=\"%e6%8e%a2%e7%a9%b6sql%e4%b8%adcase%e8%aa%9e%e5%8f%a5%e7%94%a8%e6%b3%95-riKCgzmnjr\">\u63a2\u7a76SQL\u4e2dCase\u8a9e\u53e5\u7528\u6cd5<\/h1>\n<p>\u5728SQL\u4e2d\uff0c<code>CASE<\/code>\u8a9e\u53e5\u662f\u4e00\u500b\u975e\u5e38\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u9019\u4f7f\u5f97\u5b83\u5728\u6578\u64da\u67e5\u8a62\u548c\u5831\u544a\u751f\u6210\u4e2d\u975e\u5e38\u6709\u7528\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e<code>CASE<\/code>\u8a9e\u53e5\u7684\u7528\u6cd5\uff0c\u5305\u62ec\u5176\u57fa\u672c\u8a9e\u6cd5\u3001\u4f7f\u7528\u7bc4\u4f8b\u4ee5\u53ca\u4e00\u4e9b\u5be6\u969b\u61c9\u7528\u5834\u666f\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%9f%ba%e6%9c%ac%e8%aa%9e%e6%b3%95-riKCgzmnjr\">CASE\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5<\/h2>\n<p><code>CASE<\/code>\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>\nCASE\n    WHEN condition1 THEN result1\n    WHEN condition2 THEN result2\n    ...\n    ELSE resultN\nEND\n<\/code><\/pre>\n<p>\u5728\u9019\u6bb5\u8a9e\u6cd5\u4e2d\uff0c<code>condition<\/code>\u662f\u9700\u8981\u8a55\u4f30\u7684\u689d\u4ef6\uff0c\u800c<code>result<\/code>\u5247\u662f\u7576\u689d\u4ef6\u70ba\u771f\u6642\u8fd4\u56de\u7684\u7d50\u679c\u3002\u5982\u679c\u6240\u6709\u689d\u4ef6\u90fd\u4e0d\u6eff\u8db3\uff0c\u5247\u8fd4\u56de<code>ELSE<\/code>\u5f8c\u7684\u7d50\u679c\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-riKCgzmnjr\">\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u7c21\u55ae\u7684\u7bc4\u4f8b\uff0c\u5c55\u793a\u5982\u4f55\u4f7f\u7528<code>CASE<\/code>\u8a9e\u53e5\u4f86\u6839\u64da\u5b78\u751f\u7684\u5206\u6578\u8a55\u5b9a\u7b49\u7d1a\uff1a<\/p>\n<pre><code>\nSELECT student_name,\n       score,\n       CASE\n           WHEN score &gt;= 90 THEN 'A'\n           WHEN score &gt;= 80 THEN 'B'\n           WHEN score &gt;= 70 THEN 'C'\n           WHEN score &gt;= 60 THEN 'D'\n           ELSE 'F'\n       END AS grade\nFROM students;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6839\u64da\u6bcf\u4f4d\u5b78\u751f\u7684\u5206\u6578\uff0c<code>CASE<\/code>\u8a9e\u53e5\u5c07\u8fd4\u56de\u76f8\u61c9\u7684\u7b49\u7d1a\u3002\u9019\u6a23\u7684\u67e5\u8a62\u53ef\u4ee5\u5e6b\u52a9\u6559\u5e2b\u5feb\u901f\u4e86\u89e3\u5b78\u751f\u7684\u8868\u73fe\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e9%80%b2%e9%9a%8e%e7%94%a8%e6%b3%95-riKCgzmnjr\">CASE\u8a9e\u53e5\u7684\u9032\u968e\u7528\u6cd5<\/h2>\n<p>\u9664\u4e86\u57fa\u672c\u7684\u7528\u6cd5\uff0c<code>CASE<\/code>\u8a9e\u53e5\u9084\u53ef\u4ee5\u5d4c\u5957\u4f7f\u7528\uff0c\u9019\u610f\u5473\u8457\u4f60\u53ef\u4ee5\u5728<code>CASE<\/code>\u8a9e\u53e5\u7684\u7d50\u679c\u4e2d\u518d\u4f7f\u7528\u53e6\u4e00\u500b<code>CASE<\/code>\u8a9e\u53e5\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u5d4c\u5957\u7684\u7bc4\u4f8b\uff1a<\/p>\n<pre><code>\nSELECT student_name,\n       score,\n       CASE\n           WHEN score &gt;= 60 THEN\n               CASE\n                   WHEN score &gt;= 90 THEN 'A'\n                   WHEN score &gt;= 80 THEN 'B'\n                   WHEN score &gt;= 70 THEN 'C'\n                   ELSE 'D'\n               END\n           ELSE 'F'\n       END AS grade\nFROM students;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u53ea\u6709\u7576\u5b78\u751f\u7684\u5206\u6578\u5927\u65bc\u6216\u7b49\u65bc60\u6642\uff0c\u624d\u6703\u9032\u4e00\u6b65\u8a55\u5b9a\u7b49\u7d1a\uff0c\u5426\u5247\u76f4\u63a5\u8fd4\u56de&#8217;F&#8217;\u3002<\/p>\n<h2 id=\"%e5%af%a6%e9%9a%9b%e6%87%89%e7%94%a8%e5%a0%b4%e6%99%af-riKCgzmnjr\">\u5be6\u969b\u61c9\u7528\u5834\u666f<\/h2>\n<p><code>CASE<\/code>\u8a9e\u53e5\u5728\u5be6\u969b\u61c9\u7528\u4e2d\u975e\u5e38\u5ee3\u6cdb\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u4f7f\u7528\u5834\u666f\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u5831\u544a\uff1a<\/strong>\u5728\u751f\u6210\u5831\u544a\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528<code>CASE<\/code>\u8a9e\u53e5\u4f86\u5206\u985e\u6578\u64da\uff0c\u4fbf\u65bc\u5206\u6790\u3002<\/li>\n<li><strong>\u6578\u64da\u6e05\u7406\uff1a<\/strong>\u5728\u6578\u64da\u6e05\u7406\u904e\u7a0b\u4e2d\uff0c\u53ef\u4ee5\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u4fee\u6539\u6578\u64da\u503c\u3002<\/li>\n<li><strong>\u52d5\u614b\u67e5\u8a62\uff1a<\/strong>\u5728\u67e5\u8a62\u4e2d\u6839\u64da\u7528\u6236\u8f38\u5165\u7684\u689d\u4ef6\u52d5\u614b\u751f\u6210\u7d50\u679c\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u5728\u4e00\u500b\u92b7\u552e\u5831\u544a\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528<code>CASE<\/code>\u8a9e\u53e5\u4f86\u6839\u64da\u92b7\u552e\u984d\u7684\u4e0d\u540c\u7bc4\u570d\u4f86\u5206\u985e\u92b7\u552e\u4ee3\u8868\u7684\u8868\u73fe\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-riKCgzmnjr\">\u7e3d\u7d50<\/h2>\n<p>\u7e3d\u7684\u4f86\u8aaa\uff0c<code>CASE<\/code>\u8a9e\u53e5\u662f\u4e00\u500b\u9748\u6d3b\u4e14\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5206\u6790\u5e2b\u5728SQL\u67e5\u8a62\u4e2d\u9032\u884c\u689d\u4ef6\u5224\u65b7\u548c\u6578\u64da\u5206\u985e\u3002\u7121\u8ad6\u662f\u5728\u751f\u6210\u5831\u544a\u9084\u662f\u9032\u884c\u6578\u64da\u6e05\u7406\uff0c<code>CASE<\/code>\u8a9e\u53e5\u90fd\u80fd\u63d0\u4f9b\u6975\u5927\u7684\u4fbf\u5229\u3002\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u548c\u67e5\u8a62\u512a\u5316\u6709\u9032\u4e00\u6b65\u7684\u9700\u6c42\uff0c\u8003\u616e\u4f7f\u7528<code>VPS<\/code>\u4f86\u63d0\u5347\u60a8\u7684\u6578\u64da\u8655\u7406\u80fd\u529b\uff0c\u60a8\u53ef\u4ee5\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4e86\u89e3\u66f4\u591a\u4fe1\u606f\uff0c\u7372\u53d6\u9069\u5408\u60a8\u7684\u89e3\u6c7a\u65b9\u6848\u3002<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u548c<code>\u4e91\u670d\u52a1\u5668<\/code>\u7684\u9078\u64c7\u5c07\u70ba\u60a8\u7684\u696d\u52d9\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6df1\u5165\u63a2\u7a76SQL\u4e2dCase\u8a9e\u53e5\u7684\u7528\u6cd5\uff0c\u5b78\u7fd2\u5982\u4f55\u5728\u67e5\u8a62\u4e2d\u5be6\u73fe\u689d\u4ef6\u908f\u8f2f\uff0c\u63d0\u5347\u6578\u64da\u8655\u7406\u80fd\u529b\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-188406","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/188406","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"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=188406"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/188406\/revisions"}],"predecessor-version":[{"id":188407,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/188406\/revisions\/188407"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=188406"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=188406"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=188406"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}