{"id":95348,"date":"2024-10-20T00:18:25","date_gmt":"2024-10-19T16:18:25","guid":{"rendered":"https:\/\/server.hk\/cnblog\/95348\/"},"modified":"2024-10-20T00:18:26","modified_gmt":"2024-10-19T16:18:26","slug":"oracle%e5%af%a6%e7%8f%betop-n3%e5%80%8b%e5%85%b7%e9%ab%94%e6%96%b9%e6%a1%88%e6%8f%8f%e8%bf%b0","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/95348\/","title":{"rendered":"Oracle\u5be6\u73fetop N3\u500b\u5177\u9ad4\u65b9\u6848\u63cf\u8ff0"},"content":{"rendered":"

Oracle\u5be6\u73feTop N\u7684\u4e09\u500b\u5177\u9ad4\u65b9\u6848\u63cf\u8ff0<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u67e5\u8a62Top N\u8a18\u9304\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f\u5f9e\u6027\u80fd\u512a\u5316\u9084\u662f\u6578\u64da\u5206\u6790\u7684\u89d2\u5ea6\uff0cOracle\u6578\u64da\u5eab\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u5be6\u73fe\u9019\u4e00\u529f\u80fd\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u4e09\u7a2e\u5177\u9ad4\u7684\u65b9\u6848\uff0c\u5e6b\u52a9\u7528\u6236\u6709\u6548\u5730\u5f9eOracle\u6578\u64da\u5eab\u4e2d\u63d0\u53d6Top N\u8a18\u9304\u3002<\/p>\n

\u65b9\u6848\u4e00\uff1a\u4f7f\u7528ROWNUM<\/h2>\n

ROWNUM\u662f\u4e00\u500bOracle\u7279\u6709\u7684\u4f2a\u5217\uff0c\u7528\u65bc\u9650\u5236\u67e5\u8a62\u7d50\u679c\u7684\u884c\u6578\u3002\u9019\u7a2e\u65b9\u6cd5\u7c21\u55ae\u6613\u7528\uff0c\u9069\u5408\u5c0f\u578b\u6578\u64da\u96c6\u3002<\/p>\n

SELECT * \nFROM (SELECT * FROM your_table ORDER BY your_column) \nWHERE ROWNUM <= N;<\/code><\/pre>\n
\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u9996\u5148\u5c0d\u8868\u9032\u884c\u6392\u5e8f\uff0c\u7136\u5f8c\u4f7f\u7528ROWNUM\u9650\u5236\u7d50\u679c\u96c6\u7684\u884c\u6578\u3002\u9019\u7a2e\u65b9\u6cd5\u7684\u7f3a\u9ede\u662f\uff0cROWNUM\u662f\u5728\u7d50\u679c\u96c6\u751f\u6210\u5f8c\u8a08\u7b97\u7684\uff0c\u56e0\u6b64\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\u53ef\u80fd\u6703\u5c0e\u81f4\u4e0d\u6b63\u78ba\u7684\u6392\u5e8f\u7d50\u679c\u3002<\/p>\n
\u65b9\u6848\u4e8c\uff1a\u4f7f\u7528\u5206\u6790\u51fd\u6578ROW_NUMBER()<\/h2>\n
ROW_NUMBER()\u662f\u4e00\u500b\u5206\u6790\u51fd\u6578\uff0c\u80fd\u5920\u70ba\u6bcf\u4e00\u884c\u5206\u914d\u4e00\u500b\u552f\u4e00\u7684\u5e8f\u865f\uff0c\u9019\u4f7f\u5f97\u5b83\u5728\u67e5\u8a62Top N\u8a18\u9304\u6642\u975e\u5e38\u6709\u7528\u3002<\/p>\n
SELECT * \nFROM (SELECT your_columns, ROW_NUMBER() OVER (ORDER BY your_column) AS rn \n      FROM your_table) \nWHERE rn <= N;<\/code><\/pre>\n
\u9019\u7a2e\u65b9\u6cd5\u7684\u512a\u52e2\u5728\u65bc\uff0c\u5b83\u80fd\u5920\u5728\u6392\u5e8f\u5f8c\u6b63\u78ba\u5730\u5206\u914d\u884c\u865f\uff0c\u5f9e\u800c\u78ba\u4fdd\u67e5\u8a62\u7d50\u679c\u7684\u6e96\u78ba\u6027\u3002\u4f7f\u7528ROW_NUMBER()\u9084\u53ef\u4ee5\u8f15\u9b06\u5730\u64f4\u5c55\u5230\u5206\u7d44\u67e5\u8a62\u4e2d\uff0c\u4f8b\u5982\u67e5\u8a62\u6bcf\u500b\u985e\u5225\u7684Top N\u8a18\u9304\u3002<\/p>\n
\u65b9\u6848\u4e09\uff1a\u4f7f\u7528FETCH FIRST N ROWS ONLY<\/h2>\n
\u5f9eOracle 12c\u958b\u59cb\uff0cFETCH FIRST N ROWS ONLY\u8a9e\u6cd5\u88ab\u5f15\u5165\uff0c\u9019\u4f7f\u5f97\u67e5\u8a62Top N\u8a18\u9304\u8b8a\u5f97\u66f4\u52a0\u76f4\u89c0\u3002<\/p>\n
SELECT your_columns \nFROM your_table \nORDER BY your_column \nFETCH FIRST N ROWS ONLY;<\/code><\/pre>\n
\u9019\u7a2e\u65b9\u6cd5\u7684\u512a\u9ede\u5728\u65bc\u8a9e\u6cd5\u7c21\u6f54\uff0c\u6613\u65bc\u7406\u89e3\uff0c\u4e26\u4e14\u80fd\u5920\u76f4\u63a5\u5728ORDER BY\u5b50\u53e5\u4e2d\u4f7f\u7528\u3002\u9019\u4f7f\u5f97\u67e5\u8a62\u7684\u53ef\u8b80\u6027\u5927\u5927\u63d0\u9ad8\uff0c\u4e26\u4e14\u5728\u6027\u80fd\u4e0a\u4e5f\u6709\u4e0d\u932f\u7684\u8868\u73fe\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728Oracle\u6578\u64da\u5eab\u4e2d\uff0c\u67e5\u8a62Top N\u8a18\u9304\u6709\u591a\u7a2e\u5be6\u73fe\u65b9\u6848\uff0c\u5305\u62ec\u4f7f\u7528ROWNUM\u3001ROW_NUMBER()\u5206\u6790\u51fd\u6578\u4ee5\u53caFETCH FIRST N ROWS ONLY\u8a9e\u6cd5\u3002\u6839\u64da\u5177\u9ad4\u7684\u9700\u6c42\u548c\u6578\u64da\u96c6\u7684\u5927\u5c0f\uff0c\u7528\u6236\u53ef\u4ee5\u9078\u64c7\u6700\u5408\u9069\u7684\u65b9\u6cd5\u4f86\u7372\u53d6\u6240\u9700\u7684\u6578\u64da\u3002<\/p>\n
\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\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\u670d\u52d9\u5668\u914d\u7f6e\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u6574\u9ad4\u6027\u80fd\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63a2\u7d22Oracle\u5be6\u73feTop N\u7684\u4e09\u500b\u5177\u9ad4\u65b9\u6848\uff0c\u63d0\u5347\u6578\u64da\u67e5\u8a62\u6548\u7387\uff0c\u512a\u5316\u6027\u80fd\uff0c\u52a9\u529b\u696d\u52d9\u6c7a\u7b56\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-95348","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95348","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=95348"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95348\/revisions"}],"predecessor-version":[{"id":95349,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95348\/revisions\/95349"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=95348"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=95348"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=95348"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}