{"id":175553,"date":"2024-11-08T06:50:16","date_gmt":"2024-11-07T22:50:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/175553\/"},"modified":"2024-11-08T06:50:17","modified_gmt":"2024-11-07T22:50:17","slug":"%e5%a6%82%e4%bd%95%e6%8f%90%e9%ab%98%e6%95%b8%e6%93%9a%e5%ba%abjoin%e7%9a%84%e6%95%88%e7%8e%87%ef%bc%88%e6%95%b8%e6%93%9a%e5%ba%abjoin%e6%95%88%e7%8e%87%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/175553\/","title":{"rendered":"\u5982\u4f55\u63d0\u9ad8\u6578\u64da\u5eabjoin\u7684\u6548\u7387\uff08\u6578\u64da\u5eabjoin\u6548\u7387\uff09"},"content":{"rendered":"<h1 id=\"%e5%a6%82%e4%bd%95%e6%8f%90%e9%ab%98%e6%95%b8%e6%93%9a%e5%ba%abjoin%e7%9a%84%e6%95%88%e7%8e%87%ef%bc%88%e6%95%b8%e6%93%9a%e5%ba%abjoin%e6%95%88%e7%8e%87%ef%bc%89-ImfcebvJsY\">\u5982\u4f55\u63d0\u9ad8\u6578\u64da\u5eabJOIN\u7684\u6548\u7387\uff08\u6578\u64da\u5eabJOIN\u6548\u7387\uff09<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cJOIN\u64cd\u4f5c\u662f\u7528\u4f86\u5c07\u4f86\u81ea\u5169\u500b\u6216\u591a\u500b\u8868\u7684\u6578\u64da\u7d50\u5408\u5728\u4e00\u8d77\u7684\u95dc\u9375\u6280\u8853\u3002\u96a8\u8457\u6578\u64da\u91cf\u7684\u589e\u9577\uff0cJOIN\u64cd\u4f5c\u7684\u6548\u7387\u53ef\u80fd\u6703\u53d7\u5230\u5f71\u97ff\uff0c\u5f9e\u800c\u5c0e\u81f4\u67e5\u8a62\u6027\u80fd\u4e0b\u964d\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u63d0\u9ad8\u6578\u64da\u5eabJOIN\u6548\u7387\u7684\u5e7e\u7a2e\u65b9\u6cd5\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5eab\u7ba1\u7406\u54e1\u512a\u5316\u5176\u67e5\u8a62\u6027\u80fd\u3002<\/p>\n<h2 id=\"1-%e9%81%b8%e6%93%87%e5%90%88%e9%81%a9%e7%9a%84join%e9%a1%9e%e5%9e%8b-ImfcebvJsY\">1. \u9078\u64c7\u5408\u9069\u7684JOIN\u985e\u578b<\/h2>\n<p>\u6578\u64da\u5eab\u652f\u6301\u591a\u7a2eJOIN\u985e\u578b\uff0c\u5305\u62ecINNER JOIN\u3001LEFT JOIN\u3001RIGHT JOIN\u548cFULL JOIN\u3002\u9078\u64c7\u5408\u9069\u7684JOIN\u985e\u578b\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002\u4f8b\u5982\uff0cINNER JOIN\u53ea\u8fd4\u56de\u5169\u500b\u8868\u4e2d\u5339\u914d\u7684\u884c\uff0c\u901a\u5e38\u6bd4LEFT JOIN\u6216RIGHT JOIN\u66f4\u5feb\uff0c\u56e0\u70ba\u5f8c\u8005\u9700\u8981\u8fd4\u56de\u6240\u6709\u884c\uff0c\u5373\u4f7f\u6c92\u6709\u5339\u914d\u7684\u884c\u3002<\/p>\n<h2 id=\"2-%e4%bd%bf%e7%94%a8%e7%b4%a2%e5%bc%95-ImfcebvJsY\">2. \u4f7f\u7528\u7d22\u5f15<\/h2>\n<p>\u7d22\u5f15\u662f\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u7684\u6709\u6548\u5de5\u5177\u3002\u70baJOIN\u64cd\u4f5c\u4e2d\u7684\u95dc\u9375\u5b57\u6bb5\u5275\u5efa\u7d22\u5f15\uff0c\u53ef\u4ee5\u986f\u8457\u6e1b\u5c11\u67e5\u8a62\u6240\u9700\u7684\u6642\u9593\u3002\u4ee5\u4e0b\u662f\u5275\u5efa\u7d22\u5f15\u7684\u793a\u4f8b\uff1a<\/p>\n<pre><code>CREATE INDEX idx_user_id ON orders(user_id);<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u70ba\u201corders\u201d\u8868\u4e2d\u7684\u201cuser_id\u201d\u5b57\u6bb5\u5275\u5efa\u4e86\u4e00\u500b\u7d22\u5f15\uff0c\u9019\u6a23\u5728\u9032\u884cJOIN\u64cd\u4f5c\u6642\uff0c\u6578\u64da\u5eab\u53ef\u4ee5\u66f4\u5feb\u5730\u67e5\u627e\u5339\u914d\u7684\u884c\u3002<\/p>\n<h2 id=\"3-%e9%99%90%e5%88%b6%e8%bf%94%e5%9b%9e%e7%9a%84%e5%88%97-ImfcebvJsY\">3. \u9650\u5236\u8fd4\u56de\u7684\u5217<\/h2>\n<p>\u5728\u9032\u884cJOIN\u64cd\u4f5c\u6642\uff0c\u50c5\u9078\u64c7\u9700\u8981\u7684\u5217\u800c\u4e0d\u662f\u4f7f\u7528SELECT *\uff0c\u53ef\u4ee5\u6e1b\u5c11\u6578\u64da\u50b3\u8f38\u7684\u8ca0\u64d4\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT users.name, orders.amount \nFROM users \nINNER JOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u53ea\u8fd4\u56de\u201cusers\u201d\u8868\u4e2d\u7684\u201cname\u201d\u548c\u201corders\u201d\u8868\u4e2d\u7684\u201camount\u201d\uff0c\u800c\u4e0d\u662f\u6240\u6709\u5217\uff0c\u5f9e\u800c\u63d0\u9ad8\u4e86\u6548\u7387\u3002<\/p>\n<h2 id=\"4-%e9%81%bf%e5%85%8d%e4%b8%8d%e5%bf%85%e8%a6%81%e7%9a%84join-ImfcebvJsY\">4. \u907f\u514d\u4e0d\u5fc5\u8981\u7684JOIN<\/h2>\n<p>\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u67e5\u8a62\u6642\uff0c\u61c9\u8a72\u907f\u514d\u4e0d\u5fc5\u8981\u7684JOIN\u64cd\u4f5c\u3002\u6bcf\u589e\u52a0\u4e00\u500bJOIN\uff0c\u67e5\u8a62\u7684\u8907\u96dc\u6027\u548c\u57f7\u884c\u6642\u9593\u90fd\u6703\u589e\u52a0\u3002\u53ef\u4ee5\u901a\u904e\u5206\u6790\u696d\u52d9\u9700\u6c42\uff0c\u78ba\u5b9a\u54ea\u4e9bJOIN\u662f\u5fc5\u9700\u7684\uff0c\u54ea\u4e9b\u53ef\u4ee5\u7701\u7565\u3002<\/p>\n<h2 id=\"5-%e4%bd%bf%e7%94%a8%e5%ad%90%e6%9f%a5%e8%a9%a2%e6%88%96cte-ImfcebvJsY\">5. \u4f7f\u7528\u5b50\u67e5\u8a62\u6216CTE<\/h2>\n<p>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528\u5b50\u67e5\u8a62\u6216\u516c\u7528\u8868\u8868\u9054\u5f0f\uff08CTE\uff09\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8a62\u7684\u53ef\u8b80\u6027\u548c\u6027\u80fd\u3002\u9019\u4e9b\u6280\u8853\u53ef\u4ee5\u5e6b\u52a9\u7c21\u5316\u67e5\u8a62\u908f\u8f2f\uff0c\u4e26\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\u6e1b\u5c11JOIN\u7684\u6578\u91cf\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>WITH user_orders AS (\n    SELECT user_id, SUM(amount) AS total_amount \n    FROM orders \n    GROUP BY user_id\n)\nSELECT users.name, user_orders.total_amount \nFROM users \nINNER JOIN user_orders ON users.id = user_orders.user_id;<\/code><\/pre>\n<h2 id=\"6-%e5%88%86%e6%9e%90%e6%9f%a5%e8%a9%a2%e8%a8%88%e5%8a%83-ImfcebvJsY\">6. 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