{"id":200988,"date":"2025-05-06T08:14:27","date_gmt":"2025-05-06T00:14:27","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200988\/"},"modified":"2025-05-06T08:14:27","modified_gmt":"2025-05-06T00:14:27","slug":"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8-case-when-%e8%a1%a8%e8%be%be%e5%bc%8f%e5%9c%a8-group-by-%e4%b8%ad%e6%b7%bb%e5%8a%a0%e5%88%a4%e6%96%ad%e6%9d%a1%e4%bb%b6%e7%bb%9f%e8%ae%a1%e6%95%b0%e6%8d%ae","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200988\/","title":{"rendered":"\u5982\u4f55\u4f7f\u7528 CASE WHEN \u8868\u8fbe\u5f0f\u5728 GROUP BY \u4e2d\u6dfb\u52a0\u5224\u65ad\u6761\u4ef6\u7edf\u8ba1\u6570\u636e\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u5982\u4f55\u4f7f\u7528 CASE WHEN \u8868\u8fbe\u5f0f\u5728 GROUP BY \u4e2d\u6dfb\u52a0\u5224\u65ad\u6761\u4ef6\u7edf\u8ba1\u6570\u636e\uff1f<\/h1>\n<p>\u5b66\u4e60\u8981\u52aa\u529b\uff0c\u4f46\u662f\u4e0d\u8981\u6025\uff01\u4eca\u5929\u7684\u8fd9\u7bc7\u6587\u7ae0\u5c06\u4f1a\u4ecb\u7ecd\u5230\u7b49\u7b49\u77e5\u8bc6\u70b9\uff0c\u5982\u679c\u4f60\u60f3\u6df1\u5165\u5b66\u4e60\uff0c\u53ef\u4ee5\u5173\u6ce8\u6211\uff01\u6211\u4f1a\u6301\u7eed\u66f4\u65b0\u76f8\u5173\u6587\u7ae0\u7684\uff0c\u5e0c\u671b\u5bf9\u5927\u5bb6\u90fd\u80fd\u6709\u6240\u5e2e\u52a9\uff01<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241124\/17324372266742e4ea136d3.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>\u9488\u5bf9 group by \u6dfb\u52a0\u5224\u65ad\u6761\u4ef6<\/strong><\/p>\n<p>mysql \u7684 group by \u8bed\u53e5\u53ef\u7528\u4e8e\u6839\u636e\u6307\u5b9a\u5217\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\u548c\u805a\u5408\u3002\u5f53\u9700\u8981\u5bf9\u4e0d\u540c\u5206\u7ec4\u5e94\u7528\u4e0d\u540c\u7684\u5224\u65ad\u6761\u4ef6\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528 case when \u8868\u8fbe\u5f0f\u3002<\/p>\n<p><strong>\u793a\u4f8b\u95ee\u9898\uff1a<\/strong><\/p>\n<p>\u5982\u4f55\u7edf\u8ba1 clip_url_hash \u4e3a null\u3001\u7a7a\u5b57\u7b26\u6216\u6709\u5b9e\u9645\u503c\u8fd9\u4e09\u79cd\u60c5\u51b5\u7684 count\uff1f<\/p>\n<p><strong>\u89e3\u51b3\u65b9\u6cd5\uff1a<\/strong><\/p>\n<p>\u4f7f\u7528 case when \u8868\u8fbe\u5f0f\u5982\u4e0b\uff1a<\/p>\n<pre>SELECT \n    d.checks, COUNT(d.checks)\nFROM (\n    SELECT (\n        CASE clip_url_hash\n        WHEN '' THEN '\u7a7a\u5b57\u7b26\u4e32'\n        WHEN NULL THEN 'NULL'\n        ELSE '\u6b63\u5e38\u7684' END\n    ) AS checks\n    FROM text_meta_ingest\n) AS d\nGROUP BY d.checks;<\/pre>\n<p><strong>\u89e3\u91ca\uff1a<\/strong><\/p>\n<ul>\n<li>\n<p>\u5185\u90e8\u67e5\u8be2\u4f7f\u7528 case when \u8868\u8fbe\u5f0f\u5c06 clip_url_hash \u8f6c\u6362\u4e3a\u4ee5\u4e0b\u68c0\u67e5\u503c\uff1a<\/p>\n<ul>\n<li>\u7a7a\u5b57\u7b26<\/li>\n<li>null<\/li>\n<li>\u6b63\u5e38\uff08\u957f\u5ea6\u5927\u4e8e 0\uff09<\/li>\n<\/ul>\n<\/li>\n<li>group by \u5b50\u67e5\u8be2\u7684\u7ed3\u679c\u5c06\u68c0\u67e5\u503c\u5206\u7ec4\u3002<\/li>\n<li>\u5916\u90e8\u67e5\u8be2\u5bf9\u5206\u7ec4\u540e\u7684\u7ed3\u679c\u8fdb\u884c count\u3002<\/li>\n<\/ul>\n<p>\u4eca\u5929\u5e26\u5927\u5bb6\u4e86\u89e3\u4e86\u7684\u76f8\u5173\u77e5\u8bc6\uff0c\u5e0c\u671b\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\uff1b\u5173\u4e8e\u6570\u636e\u5e93\u7684\u6280\u672f\u77e5\u8bc6\u6211\u4eec\u4f1a\u4e00\u70b9\u70b9\u6df1\u5165\u4ecb\u7ecd\uff0c\u6b22\u8fce\u5927\u5bb6\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff0c\u4e00\u8d77\u5b66\u4e60\u7f16\u7a0b~<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>\u5982\u4f55\u4f7f\u7528 CASE WHEN \u8868&#46;&#46;&#46;<\/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-200988","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200988","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=200988"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200988\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200988"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200988"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200988"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}