{"id":200548,"date":"2025-05-06T10:13:54","date_gmt":"2025-05-06T02:13:54","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200548\/"},"modified":"2025-05-06T10:13:54","modified_gmt":"2025-05-06T02:13:54","slug":"%e4%bd%bf%e7%94%a8-join-%e8%bf%98%e6%98%af%e5%a4%9a%e6%ac%a1%e6%9f%a5%e8%a1%a8%ef%bc%9f%e5%85%b3%e8%81%94%e6%9f%a5%e8%af%a2%e6%95%88%e7%8e%87%e5%93%aa%e7%a7%8d%e6%9b%b4%e9%ab%98%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200548\/","title":{"rendered":"\u4f7f\u7528 JOIN \u8fd8\u662f\u591a\u6b21\u67e5\u8868\uff1f\u5173\u8054\u67e5\u8be2\u6548\u7387\u54ea\u79cd\u66f4\u9ad8\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u4f7f\u7528 JOIN \u8fd8\u662f\u591a\u6b21\u67e5\u8868\uff1f\u5173\u8054\u67e5\u8be2\u6548\u7387\u54ea\u79cd\u66f4\u9ad8\uff1f<\/h1>\n<p>\u4f60\u5728\u5b66\u4e60\u76f8\u5173\u7684\u77e5\u8bc6\u5417\uff1f\u672c\u6587\uff0c\u4e3b\u8981\u4ecb\u7ecd\u7684\u5185\u5bb9\u5c31\u6d89\u53ca\u5230\uff0c\u5982\u679c\u4f60\u60f3\u63d0\u5347\u81ea\u5df1\u7684\u5f00\u53d1\u80fd\u529b\uff0c\u5c31\u4e0d\u8981\u9519\u8fc7\u8fd9\u7bc7\u6587\u7ae0\uff0c\u5927\u5bb6\u8981\u77e5\u9053\u7f16\u7a0b\u7406\u8bba\u57fa\u7840\u548c\u5b9e\u6218\u64cd\u4f5c\u90fd\u662f\u4e0d\u53ef\u6216\u7f3a\u7684\u54e6\uff01<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241108\/1731036648672d85e8495b8.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>\u5173\u8054\u67e5\u8be2\uff1a\u4f7f\u7528 join \u8fd8\u662f\u591a\u6b21\u67e5\u8868\uff1f<\/strong><\/p>\n<p><strong>\u9700\u6c42\uff1a<\/strong>\u83b7\u53d6\u67d0\u4e2a\u4eba\u7684\u7c89\u4e1d\u4fe1\u606f<\/p>\n<p><strong>\u8868\u7ed3\u6784\uff1a<\/strong><\/p>\n<pre>create table `auth_user` (...);\ncreate table `friendships_friendship` (...);<\/pre>\n<p><strong>\u4e24\u79cd\u65b9\u5f0f\uff1a<\/strong><\/p>\n<p><strong>\u65b9\u5f0f\u4e00\uff1a\u4f7f\u7528 join<\/strong><\/p>\n<pre>select ...\nfrom `friendships_friendship`\nleft join `auth_user` t3 on (\n    `friendships_friendship`.`from_user_id` = t3.`id`\n)\nwhere\n    `friendships_friendship`.`to_user_id` = 1;<\/pre>\n<p><strong>\u65b9\u5f0f\u4e8c\uff1a\u62c6\u5206\u6210\u4e24\u6b21\u67e5\u8868<\/strong><\/p>\n<p><strong>\u7b2c\u4e00\u6b21\u83b7\u53d6 id<\/strong><\/p>\n<pre>select ...\nfrom `friendships_friendship`\nwhere\n    `friendships_friendship`.`to_user_id` = 1;<\/pre>\n<p><strong>\u7b2c\u4e8c\u6b21\u4f7f\u7528 id \u67e5\u8be2<\/strong><\/p>\n<pre>SELECT ...\nFROM `auth_user`\nWHERE\n    `auth_user`.`id` IN (...);<\/pre>\n<p><strong>\u6548\u7387\u5bf9\u6bd4\uff1a<\/strong><\/p>\n<p>\u7b2c\u4e00\u79cd\u65b9\u5f0f\u6548\u7387\u66f4\u9ad8\uff0c\u56e0\u4e3a\u5b83\u53ea\u6267\u884c\u4e86\u4e00\u6b21\u67e5\u8be2\uff0c\u800c\u7b2c\u4e8c\u79cd\u65b9\u5f0f\u9700\u8981\u6267\u884c\u4e24\u6b21\u67e5\u8be2\u3002\u867d\u7136\u7b2c\u4e00\u79cd\u65b9\u5f0f\u4f7f\u7528\u4e86 join \u64cd\u4f5c\uff0c\u4f46\u5728 mysql \u4e2d\uff0cjoin \u4ec5\u5bf9\u6ee1\u8db3\u67e5\u8be2\u6761\u4ef6\u7684\u8bb0\u5f55\u6267\u884c\u3002\u56e0\u6b64\uff0c\u4e0e\u7b2c\u4e8c\u79cd\u65b9\u5f0f\u4f7f\u7528 in \u64cd\u4f5c\u7b26\u76f8\u6bd4\uff0c\u4e0d\u4f1a\u6709\u592a\u5927\u7684\u6027\u80fd\u5dee\u5f02\u3002<\/p>\n<p><strong>\u67e5\u8be2\u987a\u5e8f\uff1a<\/strong><\/p>\n<p>\u5bf9\u4e8e\u65b9\u5f0f\u4e00\uff0cmysql \u7684\u67e5\u8be2\u987a\u5e8f\u5982\u4e0b\uff1a<\/p>\n<ol>\n<li>\u627e\u5230\u6ee1\u8db3 friendships_friendship.to_user_id = 1 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