{"id":185310,"date":"2024-11-10T20:29:17","date_gmt":"2024-11-10T12:29:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/185310\/"},"modified":"2024-11-10T20:29:18","modified_gmt":"2024-11-10T12:29:18","slug":"%e4%bd%bf%e7%94%a8sql%e5%ad%90%e6%9f%a5%e8%a9%a2%e5%af%a6%e7%8f%be%e6%9f%a5%e6%89%be%e7%b5%90%e6%9e%9c%e4%b8%8d%e9%87%8d%e8%a4%87","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/185310\/","title":{"rendered":"\u4f7f\u7528SQL\u5b50\u67e5\u8a62\u5be6\u73fe\u67e5\u627e\u7d50\u679c\u4e0d\u91cd\u8907"},"content":{"rendered":"

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\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u4e00\u7a2e\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u9ad8\u6548\u5730\u67e5\u8a62\u548c\u64cd\u4f5c\u6578\u64da\u3002\u7576\u6211\u5011\u9700\u8981\u5f9e\u6578\u64da\u5eab\u4e2d\u7372\u53d6\u4e0d\u91cd\u8907\u7684\u67e5\u627e\u7d50\u679c\u6642\uff0c\u4f7f\u7528\u5b50\u67e5\u8a62\u662f\u4e00\u7a2e\u5e38\u898b\u4e14\u6709\u6548\u7684\u65b9\u6cd5\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u4f7f\u7528SQL\u5b50\u67e5\u8a62\u4f86\u5be6\u73fe\u67e5\u627e\u7d50\u679c\u4e0d\u91cd\u8907\uff0c\u4e26\u63d0\u4f9b\u76f8\u95dc\u7684\u793a\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n

\u4ec0\u9ebc\u662f\u5b50\u67e5\u8a62\uff1f<\/h2>\n

\u5b50\u67e5\u8a62\u662f\u6307\u5728\u4e00\u500bSQL\u67e5\u8a62\u4e2d\u5d4c\u5957\u7684\u53e6\u4e00\u500b\u67e5\u8a62\u3002\u5b50\u67e5\u8a62\u53ef\u4ee5\u7528\u65bc\u591a\u7a2e\u60c5\u6cc1\uff0c\u4f8b\u5982\u5728WHERE\u5b50\u53e5\u4e2d\u904e\u6ffe\u6578\u64da\u3001\u5728SELECT\u8a9e\u53e5\u4e2d\u9078\u64c7\u7279\u5b9a\u7684\u5217\uff0c\u6216\u5728FROM\u5b50\u53e5\u4e2d\u4f5c\u70ba\u4e00\u500b\u81e8\u6642\u8868\u4f7f\u7528\u3002\u5b50\u67e5\u8a62\u7684\u7d50\u679c\u53ef\u4ee5\u7528\u4f86\u9032\u4e00\u6b65\u7be9\u9078\u6216\u8a08\u7b97\u6578\u64da\u3002<\/p>\n

\u4f7f\u7528\u5b50\u67e5\u8a62\u67e5\u627e\u4e0d\u91cd\u8907\u7684\u7d50\u679c<\/h2>\n

\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6211\u5011\u53ef\u80fd\u9700\u8981\u5f9e\u4e00\u500b\u8868\u4e2d\u67e5\u627e\u4e0d\u91cd\u8907\u7684\u6578\u64da\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201corders\u201d\u7684\u8868\uff0c\u5176\u4e2d\u5305\u542b\u5ba2\u6236\u7684\u8a02\u55ae\u8a18\u9304\u3002\u6211\u5011\u5e0c\u671b\u67e5\u627e\u6240\u6709\u4e0b\u904e\u8a02\u55ae\u7684\u5ba2\u6236ID\uff0c\u4f46\u4e0d\u5e0c\u671b\u91cd\u8907\u986f\u793a\u76f8\u540c\u7684\u5ba2\u6236ID\u3002<\/p>\n

\u793a\u4f8b\u6578\u64da\u8868<\/h3>\n
\nCREATE TABLE orders (\n    order_id INT PRIMARY KEY,\n    customer_id INT,\n    order_date DATE\n);\n\nINSERT INTO orders (order_id, customer_id, order_date) VALUES\n(1, 101, '2023-01-01'),\n(2, 102, '2023-01-02'),\n(3, 101, '2023-01-03'),\n(4, 103, '2023-01-04'),\n(5, 102, '2023-01-05');\n<\/pre>\n
\u4f7f\u7528\u5b50\u67e5\u8a62\u67e5\u627e\u4e0d\u91cd\u8907\u7684\u5ba2\u6236ID<\/h3>\n
\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u67e5\u8a62\u4f86\u7372\u53d6\u4e0d\u91cd\u8907\u7684\u5ba2\u6236ID\uff1a<\/p>\n
\nSELECT DISTINCT customer_id\nFROM orders;\n<\/pre>\n
\u9019\u500b\u67e5\u8a62\u4f7f\u7528\u4e86DISTINCT\u95dc\u9375\u5b57\u4f86\u78ba\u4fdd\u8fd4\u56de\u7684\u7d50\u679c\u4e2d\u4e0d\u6703\u6709\u91cd\u8907\u7684\u5ba2\u6236ID\u3002\u7136\u800c\uff0c\u82e5\u6211\u5011\u60f3\u8981\u4f7f\u7528\u5b50\u67e5\u8a62\u4f86\u9054\u5230\u76f8\u540c\u7684\u6548\u679c\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
\nSELECT customer_id\nFROM (SELECT customer_id FROM orders) AS subquery\nGROUP BY customer_id;\n<\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u6211\u5011\u9996\u5148\u5728\u5b50\u67e5\u8a62\u4e2d\u9078\u64c7\u4e86\u6240\u6709\u7684\u5ba2\u6236ID\uff0c\u7136\u5f8c\u5728\u5916\u90e8\u67e5\u8a62\u4e2d\u4f7f\u7528GROUP BY\u4f86\u78ba\u4fdd\u6bcf\u500b\u5ba2\u6236ID\u53ea\u51fa\u73fe\u4e00\u6b21\u3002<\/p>\n
\u5b50\u67e5\u8a62\u7684\u512a\u52e2<\/h2>\n
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\u6ce8\u610f\u4e8b\u9805<\/h2>\n
\u5118\u7ba1\u5b50\u67e5\u8a62\u975e\u5e38\u6709\u7528\uff0c\u4f46\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u5b83\u5011\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u7684\u6027\u80fd\u3002\u7279\u5225\u662f\u5728\u8655\u7406\u5927\u91cf\u6578\u64da\u6642\uff0c\u5b50\u67e5\u8a62\u53ef\u80fd\u6703\u5c0e\u81f4\u6027\u80fd\u4e0b\u964d\u3002\u56e0\u6b64\uff0c\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u67e5\u8a62\u6642\uff0c\u958b\u767c\u8005\u61c9\u8a72\u8003\u616e\u4f7f\u7528JOIN\u64cd\u4f5c\u6216\u5176\u4ed6\u512a\u5316\u6280\u8853\u4f86\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
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