{"id":200175,"date":"2025-05-06T10:08:18","date_gmt":"2025-05-06T02:08:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200175\/"},"modified":"2025-05-06T10:08:18","modified_gmt":"2025-05-06T02:08:18","slug":"%e4%b8%ba%e4%bd%95%e5%9c%a8%e8%ae%a1%e6%95%b0%e7%bb%9f%e8%ae%a1%e6%97%b6%ef%bc%8c%e7%ac%9b%e5%8d%a1%e5%b0%94%e7%a7%af%e6%9c%89%e6%97%b6%e5%8f%8d%e8%80%8c%e6%af%94%e5%b7%a6%e8%bf%9e%e6%8e%a5%e6%95%88","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200175\/","title":{"rendered":"\u4e3a\u4f55\u5728\u8ba1\u6570\u7edf\u8ba1\u65f6\uff0c\u7b1b\u5361\u5c14\u79ef\u6709\u65f6\u53cd\u800c\u6bd4\u5de6\u8fde\u63a5\u6548\u7387\u66f4\u9ad8\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u4e3a\u4f55\u5728\u8ba1\u6570\u7edf\u8ba1\u65f6\uff0c\u7b1b\u5361\u5c14\u79ef\u6709\u65f6\u53cd\u800c\u6bd4\u5de6\u8fde\u63a5\u6548\u7387\u66f4\u9ad8\uff1f<\/h1>\n<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241027\/1730005966671dcbce3921d.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>\u4e3a\u4f55\u7b1b\u5361\u5c14\u79ef\u5728\u8ba1\u6570\u7edf\u8ba1\u65f6\u80dc\u8fc7\u5de6\u8fde\u63a5\uff1f<\/strong><\/p>\n<p>\u5728\u67d0\u4e9b\u573a\u666f\u4e0b\uff0c\u8fdb\u884c\u8ba1\u6570\u7edf\u8ba1\u65f6\uff0c\u4f7f\u7528\u7b1b\u5361\u5c14\u79ef\uff08cross join\uff09\u7684\u6548\u7387\u7adf\u7136\u9ad8\u4e8e\u5de6\u8fde\u63a5\uff08left join\uff09\uff0c\u8fd9\u4f3c\u4e4e\u8fdd\u80cc\u4e86\u5e38\u7406\u3002<\/p>\n<p><strong>\u6848\u4f8b\u5bf9\u6bd4<\/strong><\/p>\n<p>\u4ee5\u4e24\u4e2a\u8868x\u548cy\u4e3a\u4f8b\uff0cx\u8868\u670930\u4e07\u884c\u6570\u636e\uff0cy\u8868\u67092000\u884c\u6570\u636e\u3002\u6d4b\u8bd5\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n<p><strong>\u5de6\u8fde\u63a5<\/strong><\/p>\n<pre>select count(*) from x a left join y b on a.verify_user_id=b.user_id where a.state='2'<\/pre>\n<p><strong>\u7b1b\u5361\u5c14\u79ef<\/strong><\/p>\n<pre>select count(*) from X A, Y B where A.verify_user_id=B.user_id and A.state='2'<\/pre>\n<p><strong>\u6548\u7387\u5bf9\u6bd4<\/strong><\/p>\n<ul>\n<li>\u5de6\u8fde\u63a5\uff1a\u6267\u884c\u65f6\u95f42.4\u79d2<\/li>\n<li>\u7b1b\u5361\u5c14\u79ef\uff1a\u6267\u884c\u65f6\u95f40.6\u79d2<\/li>\n<\/ul>\n<p><strong>\u5206\u6790\u539f\u56e0<\/strong><\/p>\n<p>\u7b1b\u5361\u5c14\u79ef\u6548\u7387\u66f4\u9ad8\u7684\u539f\u56e0\u5728\u4e8e\uff1a<\/p>\n<ul>\n<li><strong>\u4f18\u5316\u5668\u9009\u62e9\u5dee\u5f02\uff1a<\/strong>\u5de6\u8fde\u63a5\u6307\u5b9a\u4e86x\u8868\u4e3a\u4e3b\u8868\uff0c\u5bfc\u81f4x\u8868\u4e0a\u7684\u7d22\u5f15\u65e0\u6cd5\u6709\u6548\u5730\u88ab\u4f7f\u7528\u3002\u800c\u7b1b\u5361\u5c14\u79ef\u6ca1\u6709\u6307\u5b9a\u4e3b\u8868\uff0c\u4f18\u5316\u5668\u53ef\u4ee5\u9009\u62e9\u6570\u636e\u91cf\u66f4\u5c0f\u7684y\u8868\u4f5c\u4e3a\u57fa\u7840\u8868\u3002<\/li>\n<li><strong>\u67e5\u8be2\u6761\u4ef6\u5f71\u54cd\uff1a<\/strong>\u5de6\u8fde\u63a5\u4e2d\u52a0\u5165\u4e86\u989d\u5916\u7684\u6761\u4ef6a.state=&#8217;2&#8242;, \u8fd9\u4f1a\u5bfc\u81f4\u5bf9x\u8868\u7684\u989d\u5916\u626b\u63cf\u3002\u800c\u7b1b\u5361\u5c14\u79ef\u4e2d\u5c06\u8be5\u6761\u4ef6\u4f5c\u4e3awhere\u6761\u4ef6\uff0c\u5728\u8bfb\u53d6\u6570\u636e\u524d\u8fdb\u884c\u8fc7\u6ee4\uff0c\u51cf\u5c11\u4e86\u626b\u63cf\u8303\u56f4\u3002<\/li>\n<\/ul>\n<p>\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5728\u4e0d\u540c\u573a\u666f\u4e0b\uff0c\u6548\u7387\u4f1a\u53d7\u5230\u591a\u79cd\u56e0\u7d20\u7684\u5f71\u54cd\uff0c\u5177\u4f53\u60c5\u51b5\u5e94\u5177\u4f53\u5206\u6790\u3002<\/p>\n<p><strong>\u5185\u8fde\u63a5\u7684\u4f18\u52bf<\/strong><\/p>\n<p>\u4e13\u5bb6\u5efa\u8bae\u4f18\u5148\u4f7f\u7528\u5185\u8fde\u63a5\uff08inner join\uff09\uff0c\u539f\u56e0\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li><strong>\u6548\u7387\u66f4\u9ad8\uff1a<\/strong>\u5185\u8fde\u63a5\u5b9e\u9645\u4e0a\u662f\u7b1b\u5361\u5c14\u79ef\u4e4b\u540e\u518d\u8fdb\u884c\u8fc7\u6ee4\uff0c\u56e0\u6b64\u6548\u7387\u4f1a\u9ad8\u4e8e\u5de6\u8fde\u63a5\u3002<\/li>\n<li><strong>\u907f\u514d\u7a7a\u503c\uff1a<\/strong>\u5185\u8fde\u63a5\u4e0d\u4f1a\u4ea7\u751f\u7a7a\u503c\uff0c\u8fd9\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\u975e\u5e38\u6709\u7528\u3002<\/li>\n<\/ul>\n<p>\u56e0\u6b64\uff0c\u5728\u8fdb\u884c\u8ba1\u6570\u7edf\u8ba1\u65f6\uff0c\u5e94\u6839\u636e\u5b9e\u9645\u60c5\u51b5\uff0c\u7efc\u5408\u8003\u8651\u6570\u636e\u91cf\u3001\u7d22\u5f15\u548c\u67e5\u8be2\u6761\u4ef6\u7b49\u56e0\u7d20\uff0c\u9009\u62e9\u5408\u9002\u7684join\u65b9\u5f0f\u3002<\/p>\n<p>\u4eca\u5929\u5173\u4e8e\u300a\u4e3a\u4f55\u5728\u8ba1\u6570\u7edf\u8ba1\u65f6\uff0c\u7b1b\u5361\u5c14\u79ef\u6709\u65f6\u53cd\u800c\u6bd4\u5de6\u8fde\u63a5\u6548\u7387\u66f4\u9ad8\uff1f\u300b\u7684\u5185\u5bb9\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\uff0c\u5982\u679c\u6709\u4ec0\u4e48\u7591\u95ee\u6216\u8005\u5efa\u8bae\uff0c\u53ef\u4ee5\u5728\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\u4e0b\u591a\u591a\u56de\u590d\u4ea4\u6d41\uff1b\u6587\u4e2d\u82e5\u6709\u4e0d\u6b63\u4e4b\u5904\uff0c\u4e5f\u5e0c\u671b\u56de\u590d\u7559\u8a00\u4ee5\u544a\u77e5\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>\u4e3a\u4f55\u5728\u8ba1\u6570\u7edf\u8ba1\u65f6\uff0c\u7b1b\u5361\u5c14\u79ef\u6709\u65f6\u53cd&#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-200175","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200175","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=200175"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200175\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200175"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200175"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200175"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}