{"id":168523,"date":"2024-11-06T13:05:18","date_gmt":"2024-11-06T05:05:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/168523\/"},"modified":"2024-11-06T13:05:18","modified_gmt":"2024-11-06T05:05:18","slug":"sql-%e4%b8%ad%e5%b8%b8%e7%94%a8%e7%9a%84%e5%9b%9b%e5%80%8b%e6%8e%92%e5%ba%8f%e5%87%bd%e6%95%b8%ef%bc%8c%e4%bd%a0%e7%9f%a5%e9%81%93%e5%b9%be%e5%80%8b%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/168523\/","title":{"rendered":"SQL \u4e2d\u5e38\u7528\u7684\u56db\u500b\u6392\u5e8f\u51fd\u6578\uff0c\u4f60\u77e5\u9053\u5e7e\u500b\uff1f"},"content":{"rendered":"

SQL \u4e2d\u5e38\u7528\u7684\u56db\u500b\u6392\u5e8f\u51fd\u6578\uff0c\u4f60\u77e5\u9053\u5e7e\u500b\uff1f<\/h1>\n

\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u4e2d\uff0c\u6392\u5e8f\u662f\u975e\u5e38\u91cd\u8981\u7684\u4e00\u500b\u64cd\u4f5c\u3002\u7121\u8ad6\u662f\u67e5\u8a62\u7d50\u679c\u7684\u986f\u793a\uff0c\u9084\u662f\u6578\u64da\u7684\u5206\u6790\uff0c\u6392\u5e8f\u90fd\u80fd\u5e6b\u52a9\u6211\u5011\u66f4\u597d\u5730\u7406\u89e3\u548c\u4f7f\u7528\u6578\u64da\u3002SQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u63d0\u4f9b\u4e86\u591a\u7a2e\u6392\u5e8f\u51fd\u6578\uff0c\u8b93\u4f7f\u7528\u8005\u80fd\u5920\u6839\u64da\u4e0d\u540c\u7684\u9700\u6c42\u9032\u884c\u6578\u64da\u6392\u5e8f\u3002\u672c\u6587\u5c07\u4ecb\u7d39 SQL \u4e2d\u5e38\u7528\u7684\u56db\u500b\u6392\u5e8f\u51fd\u6578\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u6df1\u5165\u5730\u4e86\u89e3\u9019\u4e9b\u5de5\u5177\u3002<\/p>\n

1. ORDER BY<\/h2>\n

ORDER BY \u662f SQL \u4e2d\u6700\u57fa\u672c\u7684\u6392\u5e8f\u51fd\u6578\u3002\u5b83\u7528\u65bc\u5c0d\u67e5\u8a62\u7d50\u679c\u9032\u884c\u6392\u5e8f\uff0c\u4e26\u4e14\u53ef\u4ee5\u6839\u64da\u4e00\u500b\u6216\u591a\u500b\u5217\u9032\u884c\u6392\u5e8f\u3002\u4f7f\u7528\u8005\u53ef\u4ee5\u6307\u5b9a\u5347\u5e8f\uff08ASC\uff09\u6216\u964d\u5e8f\uff08DESC\uff09\u4f86\u63a7\u5236\u6392\u5e8f\u7684\u65b9\u5f0f\u3002<\/p>\n

SELECT * FROM employees\nORDER BY last_name ASC, first_name DESC;<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u67e5\u8a62\u7d50\u679c\u5c07\u9996\u5148\u6839\u64da\u59d3\u6c0f\uff08last_name\uff09\u9032\u884c\u5347\u5e8f\u6392\u5e8f\uff0c\u82e5\u59d3\u6c0f\u76f8\u540c\uff0c\u5247\u6839\u64da\u540d\u5b57\uff08first_name\uff09\u9032\u884c\u964d\u5e8f\u6392\u5e8f\u3002<\/p>\n
2. GROUP BY<\/h2>\n
\u96d6\u7136 GROUP BY \u4e3b\u8981\u7528\u65bc\u5206\u7d44\u805a\u5408\uff0c\u4f46\u5b83\u4e5f\u53ef\u4ee5\u9593\u63a5\u5f71\u97ff\u6392\u5e8f\u3002\u7576\u4f7f\u7528 GROUP BY \u6642\uff0c\u901a\u5e38\u6703\u8207\u805a\u5408\u51fd\u6578\uff08\u5982 COUNT\u3001SUM \u7b49\uff09\u4e00\u8d77\u4f7f\u7528\uff0c\u4e26\u4e14\u53ef\u4ee5\u5728\u7d50\u679c\u4e2d\u4f7f\u7528 ORDER BY \u9032\u884c\u6392\u5e8f\u3002<\/p>\n
SELECT department, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department\nORDER BY employee_count DESC;<\/code><\/pre>\n
\u9019\u6bb5 SQL \u8a9e\u53e5\u5c07\u6839\u64da\u90e8\u9580\uff08department\uff09\u5206\u7d44\uff0c\u4e26\u8a08\u7b97\u6bcf\u500b\u90e8\u9580\u7684\u54e1\u5de5\u6578\u91cf\uff0c\u6700\u5f8c\u6839\u64da\u54e1\u5de5\u6578\u91cf\u9032\u884c\u964d\u5e8f\u6392\u5e8f\u3002<\/p>\n
3. RANK() \u51fd\u6578<\/h2>\n
RANK() \u51fd\u6578\u662f\u4e00\u500b\u7a97\u53e3\u51fd\u6578\uff0c\u7528\u65bc\u70ba\u67e5\u8a62\u7d50\u679c\u4e2d\u7684\u6bcf\u4e00\u884c\u5206\u914d\u4e00\u500b\u6392\u540d\u3002\u9019\u500b\u6392\u540d\u662f\u57fa\u65bc\u6307\u5b9a\u7684\u6392\u5e8f\u689d\u4ef6\uff0c\u4e26\u4e14\u5728\u9047\u5230\u76f8\u540c\u503c\u6642\u6703\u7d66\u4e88\u76f8\u540c\u7684\u6392\u540d\uff0c\u63a5\u4e0b\u4f86\u7684\u6392\u540d\u6703\u8df3\u904e\u76f8\u540c\u503c\u7684\u6578\u91cf\u3002<\/p>\n
SELECT employee_id, salary, RANK() OVER (ORDER BY salary DESC) AS salary_rank\nFROM employees;<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u6839\u64da\u85aa\u6c34\uff08salary\uff09\u9032\u884c\u964d\u5e8f\u6392\u5e8f\uff0c\u4e26\u70ba\u6bcf\u4f4d\u54e1\u5de5\u5206\u914d\u4e00\u500b\u85aa\u6c34\u6392\u540d\u3002\u5982\u679c\u6709\u591a\u4f4d\u54e1\u5de5\u7684\u85aa\u6c34\u76f8\u540c\uff0c\u4ed6\u5011\u5c07\u7372\u5f97\u76f8\u540c\u7684\u6392\u540d\uff0c\u4e0b\u4e00\u4f4d\u54e1\u5de5\u7684\u6392\u540d\u5c07\u8df3\u904e\u76f8\u540c\u7684\u6578\u91cf\u3002<\/p>\n
4. DENSE_RANK() \u51fd\u6578<\/h2>\n
DENSE_RANK() \u51fd\u6578\u8207 RANK() \u985e\u4f3c\uff0c\u4f46\u5728\u9047\u5230\u76f8\u540c\u503c\u6642\uff0c\u4e0d\u6703\u8df3\u904e\u6392\u540d\u3002\u9019\u610f\u5473\u8457\u5373\u4f7f\u6709\u591a\u4f4d\u54e1\u5de5\u7684\u85aa\u6c34\u76f8\u540c\uff0c\u4ed6\u5011\u7684\u6392\u540d\u4e5f\u6703\u662f\u9023\u7e8c\u7684\u3002<\/p>\n
SELECT employee_id, salary, DENSE_RANK() OVER (ORDER BY salary DESC) AS salary_dense_rank\nFROM employees;<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0cDENSE_RANK() \u5c07\u70ba\u6bcf\u4f4d\u54e1\u5de5\u6839\u64da\u85aa\u6c34\u9032\u884c\u964d\u5e8f\u6392\u5e8f\uff0c\u4e26\u70ba\u4ed6\u5011\u5206\u914d\u9023\u7e8c\u7684\u6392\u540d\uff0c\u5373\u4f7f\u6709\u76f8\u540c\u85aa\u6c34\u7684\u60c5\u6cc1\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728 SQL \u4e2d\uff0c\u6392\u5e8f\u51fd\u6578\u662f\u6578\u64da\u67e5\u8a62\u548c\u5206\u6790\u4e2d\u4e0d\u53ef\u6216\u7f3a\u7684\u5de5\u5177\u3002\u7121\u8ad6\u662f\u4f7f\u7528\u57fa\u672c\u7684 ORDER BY<\/code>\uff0c\u9084\u662f\u5229\u7528\u7a97\u53e3\u51fd\u6578\u5982 RANK()<\/code> \u548c DENSE_RANK()<\/code>\uff0c\u9019\u4e9b\u51fd\u6578\u90fd\u80fd\u5e6b\u52a9\u4f7f\u7528\u8005\u66f4\u6709\u6548\u5730\u7ba1\u7406\u548c\u7406\u89e3\u6578\u64da\u3002\u4e86\u89e3\u9019\u4e9b\u6392\u5e8f\u51fd\u6578\u7684\u4f7f\u7528\u65b9\u6cd5\uff0c\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u6578\u64da\u8655\u7406\u7684\u6548\u7387\u548c\u6e96\u78ba\u6027\u3002<\/p>\n
\u5982\u679c\u60a8\u5c0d\u65bc \u9999\u6e2fVPS<\/a> \u670d\u52d9\u6709\u8208\u8da3\uff0c\u6216\u60f3\u4e86\u89e3\u66f4\u591a\u95dc\u65bc \u4f3a\u670d\u5668<\/a> \u7684\u8cc7\u8a0a\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u8a73\u7d30\u8cc7\u6599\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63a2\u7d22 SQL \u4e2d\u56db\u500b\u5e38\u7528\u7684\u6392\u5e8f\u51fd\u6578\uff0c\u4e86\u89e3\u5982\u4f55\u6709\u6548\u5730\u7d44\u7e54\u548c\u67e5\u8a62\u6578\u64da\uff0c\u63d0\u5347\u6578\u64da\u8655\u7406\u6548\u7387\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-168523","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168523","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"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=168523"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168523\/revisions"}],"predecessor-version":[{"id":168524,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168523\/revisions\/168524"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=168523"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=168523"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=168523"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}