{"id":95350,"date":"2024-10-20T00:19:15","date_gmt":"2024-10-19T16:19:15","guid":{"rendered":"https:\/\/server.hk\/cnblog\/95350\/"},"modified":"2024-10-20T00:19:15","modified_gmt":"2024-10-19T16:19:15","slug":"oracle%e5%af%a6%e7%8f%betop-n%e7%9a%84%e5%af%a6%e9%9a%9b%e6%93%8d%e4%bd%9c%e6%ad%a5%e9%a9%9f%e6%8f%8f%e8%bf%b0","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/95350\/","title":{"rendered":"Oracle\u5be6\u73fetop N\u7684\u5be6\u969b\u64cd\u4f5c\u6b65\u9a5f\u63cf\u8ff0"},"content":{"rendered":"<h1 id=\"oracle%e5%af%a6%e7%8f%betop-n%e7%9a%84%e5%af%a6%e9%9a%9b%e6%93%8d%e4%bd%9c%e6%ad%a5%e9%a9%9f%e6%8f%8f%e8%bf%b0-HddsmtICCu\">Oracle\u5be6\u73feTop N\u7684\u5be6\u969b\u64cd\u4f5c\u6b65\u9a5f\u63cf\u8ff0<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u7372\u53d6Top N\u8a18\u9304\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f\u70ba\u4e86\u5206\u6790\u6578\u64da\u9084\u662f\u751f\u6210\u5831\u544a\uff0cOracle\u6578\u64da\u5eab\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u5be6\u73fe\u9019\u4e00\u76ee\u6a19\u3002\u672c\u6587\u5c07\u8a73\u7d30\u4ecb\u7d39\u5728Oracle\u4e2d\u5be6\u73feTop N\u7684\u5177\u9ad4\u64cd\u4f5c\u6b65\u9a5f\uff0c\u4e26\u63d0\u4f9b\u76f8\u61c9\u7684\u793a\u4f8b\u4ee3\u78bc\u3002<\/p>\n<h2 id=\"1-%e4%bd%bf%e7%94%a8rownum%e7%8d%b2%e5%8f%96top-n%e8%a8%98%e9%8c%84-HddsmtICCu\">1. \u4f7f\u7528ROWNUM\u7372\u53d6Top N\u8a18\u9304<\/h2>\n<p>\u5728Oracle\u4e2d\uff0c\u6700\u7c21\u55ae\u7684\u65b9\u6cd5\u4e4b\u4e00\u662f\u4f7f\u7528ROWNUM\u3002ROWNUM\u662f\u4e00\u500b\u865b\u64ec\u5217\uff0c\u8868\u793a\u67e5\u8a62\u7d50\u679c\u4e2d\u7684\u884c\u865f\u3002\u4ee5\u4e0b\u662f\u4f7f\u7528ROWNUM\u7372\u53d6Top N\u8a18\u9304\u7684\u57fa\u672c\u8a9e\u6cd5\uff1a<\/p>\n<pre><code>SELECT * \nFROM (SELECT * FROM \u8868\u540d ORDER BY \u6392\u5e8f\u5217) \nWHERE ROWNUM &lt;= N;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201cemployees\u201d\u7684\u8868\uff0c\u4e26\u5e0c\u671b\u7372\u53d6\u85aa\u6c34\u6700\u9ad8\u7684\u524d5\u540d\u54e1\u5de5\uff1a<\/p>\n<pre><code>SELECT * \nFROM (SELECT * FROM employees ORDER BY salary DESC) \nWHERE ROWNUM &lt;= 5;<\/code><\/pre>\n<h2 id=\"2-%e4%bd%bf%e7%94%a8%e5%88%86%e6%9e%90%e5%87%bd%e6%95%b8row_number%e7%8d%b2%e5%8f%96top-n%e8%a8%98%e9%8c%84-HddsmtICCu\">2. \u4f7f\u7528\u5206\u6790\u51fd\u6578ROW_NUMBER()\u7372\u53d6Top N\u8a18\u9304<\/h2>\n<p>\u53e6\u4e00\u7a2e\u66f4\u9748\u6d3b\u7684\u65b9\u6cd5\u662f\u4f7f\u7528\u5206\u6790\u51fd\u6578ROW_NUMBER()\u3002\u9019\u7a2e\u65b9\u6cd5\u5141\u8a31\u6211\u5011\u5728\u5206\u7d44\u7684\u57fa\u790e\u4e0a\u7372\u53d6Top N\u8a18\u9304\u3002\u4ee5\u4e0b\u662f\u4f7f\u7528ROW_NUMBER()\u7684\u57fa\u672c\u8a9e\u6cd5\uff1a<\/p>\n<pre><code>SELECT * \nFROM (SELECT column1, column2, ROW_NUMBER() OVER (PARTITION BY \u5206\u7d44\u5217 ORDER BY \u6392\u5e8f\u5217) AS rn \n      FROM \u8868\u540d) \nWHERE rn &lt;= N;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u5e0c\u671b\u7372\u53d6\u6bcf\u500b\u90e8\u9580\u4e2d\u85aa\u6c34\u6700\u9ad8\u7684\u524d2\u540d\u54e1\u5de5\uff1a<\/p>\n<pre><code>SELECT * \nFROM (SELECT employee_id, department_id, salary, \n             ROW_NUMBER() OVER (PARTITION BY department_id ORDER BY salary DESC) AS rn \n      FROM employees) \nWHERE rn &lt;= 2;<\/code><\/pre>\n<h2 id=\"3-%e4%bd%bf%e7%94%a8fetch-first-n-rows-only-HddsmtICCu\">3. \u4f7f\u7528FETCH FIRST N ROWS ONLY<\/h2>\n<p>\u5f9eOracle 12c\u958b\u59cb\uff0c\u9084\u53ef\u4ee5\u4f7f\u7528FETCH FIRST N ROWS ONLY\u8a9e\u6cd5\u4f86\u7372\u53d6Top N\u8a18\u9304\u3002\u9019\u7a2e\u65b9\u6cd5\u66f4\u70ba\u7c21\u6f54\uff0c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT * \nFROM \u8868\u540d \nORDER BY \u6392\u5e8f\u5217 \nFETCH FIRST N ROWS ONLY;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u7372\u53d6\u85aa\u6c34\u6700\u9ad8\u7684\u524d5\u540d\u54e1\u5de5\u7684\u67e5\u8a62\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT * \nFROM employees \nORDER BY salary DESC \nFETCH FIRST 5 ROWS ONLY;<\/code><\/pre>\n<h2 id=\"4-%e5%b0%8f%e7%b5%90-HddsmtICCu\">4. \u5c0f\u7d50<\/h2>\n<p>\u5728Oracle\u4e2d\uff0c\u6709\u591a\u7a2e\u65b9\u6cd5\u53ef\u4ee5\u5be6\u73feTop N\u8a18\u9304\u7684\u67e5\u8a62\u3002\u4f7f\u7528ROWNUM\u3001ROW_NUMBER()\u548cFETCH FIRST N ROWS ONLY\u7b49\u65b9\u6cd5\uff0c\u5404\u6709\u5176\u9069\u7528\u5834\u666f\u3002\u6839\u64da\u5177\u9ad4\u9700\u6c42\u9078\u64c7\u5408\u9069\u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u548c\u53ef\u8b80\u6027\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-HddsmtICCu\">\u7e3d\u7d50<\/h2>\n<p>\u672c\u6587\u4ecb\u7d39\u4e86\u5728Oracle\u4e2d\u5be6\u73feTop N\u8a18\u9304\u7684\u5e7e\u7a2e\u65b9\u6cd5\uff0c\u5305\u62ec\u4f7f\u7528ROWNUM\u3001ROW_NUMBER()\u548cFETCH FIRST N ROWS ONLY\u3002\u9019\u4e9b\u6280\u8853\u5c0d\u65bc\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u751f\u6210\u975e\u5e38\u6709\u7528\u3002\u5982\u679c\u60a8\u9700\u8981\u7a69\u5b9a\u7684\u6578\u64da\u5eab\u74b0\u5883\u4f86\u904b\u884c\u9019\u4e9b\u67e5\u8a62\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u6216<a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a>\u4f86\u652f\u6301\u60a8\u7684\u696d\u52d9\u9700\u6c42\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3Oracle\u4e2d\u5be6\u73feTop N\u67e5\u8a62\u7684\u5177\u9ad4\u64cd\u4f5c\u6b65\u9a5f\uff0c\u63d0\u5347\u6578\u64da\u6aa2\u7d22\u6548\u7387\uff0c\u7c21\u5316\u6578\u64da\u5206\u6790\u904e\u7a0b\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-95350","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95350","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=95350"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95350\/revisions"}],"predecessor-version":[{"id":95351,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/95350\/revisions\/95351"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=95350"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=95350"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=95350"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}