{"id":182978,"date":"2024-11-10T00:55:21","date_gmt":"2024-11-09T16:55:21","guid":{"rendered":"https:\/\/server.hk\/cnblog\/182978\/"},"modified":"2024-11-10T00:55:22","modified_gmt":"2024-11-09T16:55:22","slug":"%e5%af%a6%e7%8f%bemysql-top-n%e6%9f%a5%e8%a9%a2%e7%9a%84%e6%ad%a5%e9%a9%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/182978\/","title":{"rendered":"\u5be6\u73feMySQL top n\u67e5\u8a62\u7684\u6b65\u9a5f"},"content":{"rendered":"

\u5be6\u73feMySQL top n\u67e5\u8a62\u7684\u6b65\u9a5f<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u806f\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u7576\u6211\u5011\u9700\u8981\u5f9e\u6578\u64da\u96c6\u4e2d\u63d0\u53d6\u7279\u5b9a\u6578\u91cf\u7684\u8a18\u9304\u6642\uff0ctop n\u67e5\u8a62\u4fbf\u6210\u70ba\u4e86\u4e00\u500b\u91cd\u8981\u7684\u64cd\u4f5c\u3002\u9019\u7bc7\u6587\u7ae0\u5c07\u4ecb\u7d39\u5982\u4f55\u5728MySQL\u4e2d\u5be6\u73fetop n\u67e5\u8a62\u7684\u6b65\u9a5f\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u7bc4\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n

\u4ec0\u9ebc\u662fTop N\u67e5\u8a62\uff1f<\/h2>\n

Top N\u67e5\u8a62\u662f\u6307\u5f9e\u4e00\u500b\u6578\u64da\u96c6\u6216\u8868\u4e2d\u9078\u64c7\u524dN\u689d\u8a18\u9304\uff0c\u9019\u4e9b\u8a18\u9304\u901a\u5e38\u662f\u6839\u64da\u67d0\u500b\u7279\u5b9a\u7684\u6392\u5e8f\u689d\u4ef6\u4f86\u7be9\u9078\u7684\u3002\u4f8b\u5982\uff0c\u9078\u64c7\u92b7\u552e\u984d\u6700\u9ad8\u7684\u524d10\u500b\u7522\u54c1\uff0c\u6216\u662f\u6700\u8fd1\u767b\u9304\u7684\u524d5\u500b\u7528\u6236\u3002\u9019\u985e\u67e5\u8a62\u5728\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u4e2d\u975e\u5e38\u5e38\u898b\u3002<\/p>\n

\u5be6\u73feTop N\u67e5\u8a62\u7684\u57fa\u672c\u6b65\u9a5f<\/h2>\n

1. \u78ba\u5b9a\u67e5\u8a62\u7684\u6578\u64da\u8868<\/h3>\n

\u9996\u5148\uff0c\u60a8\u9700\u8981\u78ba\u5b9a\u8981\u67e5\u8a62\u7684\u6578\u64da\u8868\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70baproducts<\/code>\u7684\u8868\uff0c\u8a72\u8868\u5305\u542b\u7522\u54c1\u7684\u8a73\u7d30\u4fe1\u606f\uff0c\u5305\u62ec\u7522\u54c1\u540d\u7a31\u548c\u92b7\u552e\u984d\u3002<\/p>\n

2. \u4f7f\u7528ORDER BY\u9032\u884c\u6392\u5e8f<\/h3>\n

\u70ba\u4e86\u7372\u53d6\u524dN\u689d\u8a18\u9304\uff0c\u60a8\u9700\u8981\u6839\u64da\u67d0\u500b\u5b57\u6bb5\u9032\u884c\u6392\u5e8f\u3002\u4f7f\u7528ORDER BY<\/code>\u5b50\u53e5\u53ef\u4ee5\u5be6\u73fe\u9019\u4e00\u9ede\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u6839\u64da\u92b7\u552e\u984d\u9032\u884c\u6392\u5e8f\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u8a9e\u53e5\uff1a<\/p>\n

SELECT * FROM products ORDER BY sales DESC;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u7522\u54c1\uff0c\u4e26\u6839\u64da\u92b7\u552e\u984d\u5f9e\u9ad8\u5230\u4f4e\u9032\u884c\u6392\u5e8f\u3002<\/p>\n
3. \u9650\u5236\u67e5\u8a62\u7d50\u679c\u7684\u6578\u91cf<\/h3>\n
\u63a5\u4e0b\u4f86\uff0c\u60a8\u9700\u8981\u9650\u5236\u67e5\u8a62\u7d50\u679c\u7684\u6578\u91cf\u3002\u9019\u53ef\u4ee5\u901a\u904eLIMIT<\/code>\u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u7372\u53d6\u92b7\u552e\u984d\u6700\u9ad8\u7684\u524d10\u500b\u7522\u54c1\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u8a9e\u53e5\uff1a<\/p>\n
SELECT * FROM products ORDER BY sales DESC LIMIT 10;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u92b7\u552e\u984d\u6700\u9ad8\u768410\u500b\u7522\u54c1\u3002<\/p>\n
4. \u7d50\u5408WHERE\u5b50\u53e5\u9032\u884c\u7be9\u9078\uff08\u53ef\u9078\uff09<\/h3>\n
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SELECT * FROM products WHERE category = 'Electronics' ORDER BY sales DESC LIMIT 5;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u985e\u5225\u70ba\u201cElectronics\u201d\u7684\u92b7\u552e\u984d\u6700\u9ad8\u76845\u500b\u7522\u54c1\u3002<\/p>\n
\u7bc4\u4f8b\uff1a\u5be6\u73feTop N\u67e5\u8a62<\/h2>\n
\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70baemployees<\/code>\u7684\u8868\uff0c\u8a72\u8868\u5305\u542b\u54e1\u5de5\u7684\u59d3\u540d\u548c\u5de5\u8cc7\u3002\u82e5\u8981\u67e5\u8a62\u5de5\u8cc7\u6700\u9ad8\u7684\u524d3\u540d\u54e1\u5de5\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u8a9e\u53e5\uff1a<\/p>\n
SELECT * FROM employees ORDER BY salary DESC LIMIT 3;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u5de5\u8cc7\u6700\u9ad8\u76843\u540d\u54e1\u5de5\u7684\u6240\u6709\u4fe1\u606f\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728MySQL\u4e2d\u5be6\u73fetop n\u67e5\u8a62\u7684\u904e\u7a0b\u76f8\u5c0d\u7c21\u55ae\uff0c\u4e3b\u8981\u5305\u62ec\u78ba\u5b9a\u6578\u64da\u8868\u3001\u4f7f\u7528ORDER BY<\/code>\u9032\u884c\u6392\u5e8f\u3001\u4f7f\u7528LIMIT<\/code>\u9650\u5236\u7d50\u679c\u6578\u91cf\uff0c\u4ee5\u53ca\u53ef\u9078\u7684WHERE<\/code>\u5b50\u53e5\u9032\u884c\u7be9\u9078\u3002\u9019\u4e9b\u6b65\u9a5f\u53ef\u4ee5\u5e6b\u52a9\u60a8\u5feb\u901f\u7372\u53d6\u6240\u9700\u7684\u6578\u64da\uff0c\u4e26\u5728\u6578\u64da\u5206\u6790\u4e2d\u767c\u63ee\u91cd\u8981\u4f5c\u7528\u3002<\/p>\n
\u5982\u679c\u60a8\u9700\u8981\u7a69\u5b9a\u7684\u6578\u64da\u5eab\u74b0\u5883\u4f86\u57f7\u884c\u9019\u4e9b\u67e5\u8a62\uff0c\u8003\u616e\u4f7f\u7528\u9999\u6e2fVPS<\/a>\u6216\u9999\u6e2f\u4f3a\u670d\u5668<\/a>\u4f86\u652f\u6301\u60a8\u7684\u696d\u52d9\u9700\u6c42\u3002\u7121\u8ad6\u662f\u6578\u64da\u5b58\u5132\u9084\u662f\u61c9\u7528\u90e8\u7f72\uff0c\u9078\u64c7\u5408\u9069\u7684\u4f3a\u670d\u5668\u90fd\u80fd\u63d0\u9ad8\u60a8\u7684\u5de5\u4f5c\u6548\u7387\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4e86\u89e3\u5982\u4f55\u5728MySQL\u4e2d\u5be6\u73fetop n\u67e5\u8a62\u7684\u6b65\u9a5f\uff0c\u8f15\u9b06\u7372\u53d6\u6240\u9700\u7684\u524dN\u689d\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-182978","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/182978","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=182978"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/182978\/revisions"}],"predecessor-version":[{"id":182979,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/182978\/revisions\/182979"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=182978"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=182978"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=182978"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}