{"id":187610,"date":"2024-11-11T15:42:20","date_gmt":"2024-11-11T07:42:20","guid":{"rendered":"https:\/\/server.hk\/cnblog\/187610\/"},"modified":"2024-11-11T15:42:20","modified_gmt":"2024-11-11T07:42:20","slug":"%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5%e5%b5%8c%e5%a5%97%e5%84%aa%e5%8c%96%e6%8a%80%e5%b7%a7%e5%85%a8%e9%9d%a2%e6%8e%a2%e7%a9%b6-%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5%e5%b5%8c%e5%a5%97","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/187610\/","title":{"rendered":"\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957\u512a\u5316\u6280\u5de7\u5168\u9762\u63a2\u7a76 (\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957)"},"content":{"rendered":"

\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957\u512a\u5316\u6280\u5de7\u5168\u9762\u63a2\u7a76<\/h1>\n

\u5728\u73fe\u4eca\u7684\u6578\u64da\u9a45\u52d5\u6642\u4ee3\uff0c\u6578\u64da\u5eab\u7684\u6027\u80fd\u5c0d\u65bc\u61c9\u7528\u7a0b\u5e8f\u7684\u6574\u9ad4\u6548\u7387\u81f3\u95dc\u91cd\u8981\u3002\u6578\u64da\u5eab\u8a9e\u53e5\u7684\u5d4c\u5957\uff08Nested Queries\uff09\u662f\u4e00\u7a2e\u5e38\u898b\u7684\u67e5\u8a62\u65b9\u5f0f\uff0c\u4f46\u5982\u679c\u4e0d\u52a0\u4ee5\u512a\u5316\uff0c\u53ef\u80fd\u6703\u5c0e\u81f4\u6027\u80fd\u74f6\u9838\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957\u7684\u512a\u5316\u6280\u5de7\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u63d0\u5347\u67e5\u8a62\u6548\u7387\u3002<\/p>\n

\u4ec0\u9ebc\u662f\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957\uff1f<\/h2>\n

\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957\u662f\u6307\u5728\u4e00\u500b\u67e5\u8a62\u4e2d\u4f7f\u7528\u53e6\u4e00\u500b\u67e5\u8a62\u7684\u7d50\u679c\u3002\u9019\u7a2e\u65b9\u5f0f\u901a\u5e38\u7528\u65bc\u9700\u8981\u5f9e\u591a\u500b\u8868\u4e2d\u63d0\u53d6\u6578\u64da\u7684\u60c5\u6cc1\u3002\u5d4c\u5957\u67e5\u8a62\u53ef\u4ee5\u5206\u70ba\u5169\u985e\uff1a\u5167\u90e8\u67e5\u8a62<\/strong>\uff08Subquery\uff09\u548c\u806f\u63a5\u67e5\u8a62<\/strong>\uff08Join\uff09\u3002<\/p>\n

\u5167\u90e8\u67e5\u8a62<\/h3>\n

\u5167\u90e8\u67e5\u8a62\u662f\u6307\u5728\u4e3b\u67e5\u8a62\u4e2d\u5d4c\u5165\u7684\u67e5\u8a62\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u7c21\u55ae\u7684\u4f8b\u5b50\uff1a<\/p>\n

SELECT name FROM employees WHERE department_id IN (SELECT id FROM departments WHERE location = 'Hong Kong');<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u5167\u90e8\u67e5\u8a62\u9996\u5148\u7372\u53d6\u4f4d\u65bc\u9999\u6e2f\u7684\u90e8\u9580ID\uff0c\u7136\u5f8c\u4e3b\u67e5\u8a62\u6839\u64da\u9019\u4e9bID\u7372\u53d6\u54e1\u5de5\u59d3\u540d\u3002<\/p>\n
\u806f\u63a5\u67e5\u8a62<\/h3>\n
\u806f\u63a5\u67e5\u8a62\u5247\u662f\u901a\u904e\u806f\u63a5\u591a\u500b\u8868\u4f86\u7372\u53d6\u6240\u9700\u6578\u64da\u3002\u4ee5\u4e0b\u662f\u4f7f\u7528\u806f\u63a5\u7684\u4f8b\u5b50\uff1a<\/p>\n
SELECT e.name FROM employees e JOIN departments d ON e.department_id = d.id WHERE d.location = 'Hong Kong';<\/code><\/pre>\n
\u9019\u7a2e\u65b9\u5f0f\u901a\u5e38\u6bd4\u5167\u90e8\u67e5\u8a62\u66f4\u9ad8\u6548\uff0c\u56e0\u70ba\u6578\u64da\u5eab\u53ef\u4ee5\u66f4\u597d\u5730\u512a\u5316\u806f\u63a5\u64cd\u4f5c\u3002<\/p>\n
\u6578\u64da\u5eab\u8a9e\u53e5\u5d4c\u5957\u7684\u512a\u5316\u6280\u5de7<\/h2>\n
1. \u4f7f\u7528\u806f\u63a5\u4ee3\u66ff\u5167\u90e8\u67e5\u8a62<\/h3>\n
\u5982\u524d\u6240\u8ff0\uff0c\u806f\u63a5\u67e5\u8a62\u901a\u5e38\u6bd4\u5167\u90e8\u67e5\u8a62\u66f4\u9ad8\u6548\u3002\u7576\u53ef\u80fd\u6642\uff0c\u61c9\u512a\u5148\u8003\u616e\u4f7f\u7528\u806f\u63a5\u4f86\u7372\u53d6\u6578\u64da\u3002\u9019\u4e0d\u50c5\u80fd\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\uff0c\u9084\u80fd\u6e1b\u5c11\u6578\u64da\u5eab\u7684\u8ca0\u64d4\u3002<\/p>\n
2. \u9650\u5236\u8fd4\u56de\u7684\u6578\u64da\u91cf<\/h3>\n
\u5728\u5d4c\u5957\u67e5\u8a62\u4e2d\uff0c\u61c9\u76e1\u91cf\u9650\u5236\u8fd4\u56de\u7684\u6578\u64da\u91cf\u3002\u4f8b\u5982\uff0c\u4f7f\u7528 LIMIT<\/code> \u5b50\u53e5\u4f86\u9650\u5236\u7d50\u679c\u96c6\u7684\u5927\u5c0f\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u6578\u64da\u5eab\u7684\u8655\u7406\u6642\u9593\u3002<\/p>\n
SELECT name FROM employees WHERE department_id IN (SELECT id FROM departments WHERE location = 'Hong Kong' LIMIT 10);<\/code><\/pre>\n
3. \u4f7f\u7528\u7d22\u5f15<\/h3>\n
\u70ba\u4e86\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\uff0c\u61c9\u5728\u7d93\u5e38\u7528\u4f5c\u67e5\u8a62\u689d\u4ef6\u7684\u5217\u4e0a\u5275\u5efa\u7d22\u5f15\u3002\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u52a0\u5feb\u6578\u64da\u6aa2\u7d22\u901f\u5ea6\uff0c\u7279\u5225\u662f\u5728\u8655\u7406\u5927\u578b\u6578\u64da\u96c6\u6642\u3002<\/p>\n
4. \u907f\u514d\u4e0d\u5fc5\u8981\u7684\u5d4c\u5957<\/h3>\n
\u5728\u8a2d\u8a08\u67e5\u8a62\u6642\uff0c\u61c9\u907f\u514d\u4e0d\u5fc5\u8981\u7684\u5d4c\u5957\u3002\u904e\u591a\u7684\u5d4c\u5957\u4e0d\u50c5\u6703\u4f7f\u67e5\u8a62\u8b8a\u5f97\u8907\u96dc\uff0c\u9084\u6703\u5f71\u97ff\u6027\u80fd\u3002\u61c9\u8a72\u8003\u616e\u5c07\u591a\u500b\u67e5\u8a62\u5408\u4f75\u70ba\u4e00\u500b\u67e5\u8a62\uff0c\u6216\u4f7f\u7528\u81e8\u6642\u8868\u4f86\u5b58\u5132\u4e2d\u9593\u7d50\u679c\u3002<\/p>\n
5. \u5206\u6790\u67e5\u8a62\u8a08\u5283<\/h3>\n
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\u7d50\u8ad6<\/h2>\n
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\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u61c9\u7528\u7a0b\u5e8f\uff0c\u9078\u64c7\u5408\u9069\u7684 VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u81f3\u95dc\u91cd\u8981\u3002\u7121\u8ad6\u662f \u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u985e\u578b\u7684 \u4f3a\u670d\u5668<\/a>\uff0c\u90fd\u80fd\u70ba\u60a8\u7684\u6578\u64da\u5eab\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\uff0c\u78ba\u4fdd\u9ad8\u6548\u904b\u884c\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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