{"id":172833,"date":"2024-11-07T15:27:25","date_gmt":"2024-11-07T07:27:25","guid":{"rendered":"https:\/\/server.hk\/cnblog\/172833\/"},"modified":"2024-11-07T15:27:26","modified_gmt":"2024-11-07T07:27:26","slug":"%e5%a6%82%e4%bd%95%e6%9f%a5%e8%a9%a2%e4%b8%80%e5%bc%b5%e8%a1%a8%e4%b8%ad%e7%9a%84%e4%b8%8d%e9%87%8d%e8%a4%87%e6%95%b8%e6%93%9a%e5%ba%ab%ef%bc%9f-%e6%9f%a5%e8%a9%a2%e4%b8%80%e5%bc%b5%e8%a1%a8%e4%b8%ad","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/172833\/","title":{"rendered":"\u5982\u4f55\u67e5\u8a62\u4e00\u5f35\u8868\u4e2d\u7684\u4e0d\u91cd\u8907\u6578\u64da\u5eab\uff1f (\u67e5\u8a62\u4e00\u5f35\u8868\u4e2d\u9664\u53bb\u91cd\u8907\u7684\u6578\u64da\u5eab)"},"content":{"rendered":"

\u5982\u4f55\u67e5\u8a62\u4e00\u5f35\u8868\u4e2d\u7684\u4e0d\u91cd\u8907\u6578\u64da\u5eab\uff1f<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u6578\u64da\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f\u70ba\u4e86\u6578\u64da\u5206\u6790\u3001\u5831\u544a\u751f\u6210\uff0c\u9084\u662f\u70ba\u4e86\u4fdd\u6301\u6578\u64da\u7684\u6574\u6f54\u6027\uff0c\u53bb\u9664\u91cd\u8907\u6578\u64da\u90fd\u662f\u4e00\u500b\u91cd\u8981\u7684\u6b65\u9a5f\u3002\u672c\u6587\u5c07\u4ecb\u7d39\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u67e5\u8a62\u4e00\u5f35\u8868\u4e2d\u7684\u4e0d\u91cd\u8907\u6578\u64da\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684 SQL \u67e5\u8a62\u793a\u4f8b\u3002<\/p>\n

\u7406\u89e3\u91cd\u8907\u6578\u64da\u7684\u6982\u5ff5<\/h2>\n

\u91cd\u8907\u6578\u64da\u662f\u6307\u5728\u6578\u64da\u5eab\u8868\u4e2d\u51fa\u73fe\u591a\u6b21\u7684\u76f8\u540c\u6578\u64da\u884c\u3002\u9019\u53ef\u80fd\u662f\u7531\u65bc\u6578\u64da\u8f38\u5165\u932f\u8aa4\u3001\u6578\u64da\u5408\u4f75\u6216\u5176\u4ed6\u539f\u56e0\u9020\u6210\u7684\u3002\u91cd\u8907\u6578\u64da\u4e0d\u50c5\u6703\u5f71\u97ff\u6578\u64da\u7684\u6e96\u78ba\u6027\uff0c\u9084\u53ef\u80fd\u5c0e\u81f4\u67e5\u8a62\u7d50\u679c\u7684\u504f\u5dee\u3002\u56e0\u6b64\uff0c\u8b58\u5225\u548c\u53bb\u9664\u91cd\u8907\u6578\u64da\u662f\u6578\u64da\u7ba1\u7406\u4e2d\u7684\u4e00\u500b\u91cd\u8981\u4efb\u52d9\u3002<\/p>\n

\u4f7f\u7528 SQL \u67e5\u8a62\u4e0d\u91cd\u8907\u6578\u64da<\/h2>\n

\u5728 SQL \u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528 SELECT DISTINCT<\/code> \u8a9e\u53e5\u4f86\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u6578\u64da\u3002\u9019\u500b\u8a9e\u53e5\u6703\u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u6240\u6709\u4e0d\u540c\u7684\u503c\u3002\u4ee5\u4e0b\u662f\u57fa\u672c\u7684\u8a9e\u6cd5\uff1a<\/p>\n

SELECT DISTINCT column1, column2, ...\nFROM table_name;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba customers<\/code> \u7684\u8868\uff0c\u4e26\u4e14\u6211\u5011\u60f3\u8981\u67e5\u8a62\u6240\u6709\u4e0d\u91cd\u8907\u7684\u57ce\u5e02\u540d\u7a31\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u67e5\u8a62\uff1a<\/p>\n
SELECT DISTINCT city\nFROM customers;<\/code><\/pre>\n
\u67e5\u8a62\u591a\u500b\u5217\u7684\u4e0d\u91cd\u8907\u6578\u64da<\/h3>\n
\u5982\u679c\u9700\u8981\u67e5\u8a62\u591a\u500b\u5217\u7684\u4e0d\u91cd\u8907\u6578\u64da\uff0c\u53ef\u4ee5\u5728 SELECT DISTINCT<\/code> \u8a9e\u53e5\u4e2d\u5217\u51fa\u591a\u500b\u5217\u540d\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT DISTINCT first_name, last_name\nFROM customers;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6240\u6709\u4e0d\u91cd\u8907\u7684\u540d\u5b57\u548c\u59d3\u6c0f\u7d44\u5408\u3002<\/p>\n
\u4f7f\u7528 GROUP BY \u4f86\u67e5\u8a62\u4e0d\u91cd\u8907\u6578\u64da<\/h2>\n
\u9664\u4e86 SELECT DISTINCT<\/code>\uff0c\u9084\u53ef\u4ee5\u4f7f\u7528 GROUP BY<\/code> \u8a9e\u53e5\u4f86\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u6578\u64da\u3002\u9019\u7a2e\u65b9\u6cd5\u901a\u5e38\u7528\u65bc\u9700\u8981\u9032\u884c\u805a\u5408\u8a08\u7b97\u7684\u60c5\u6cc1\u3002\u4ee5\u4e0b\u662f\u57fa\u672c\u7684\u8a9e\u6cd5\uff1a<\/p>\n
SELECT column1, COUNT(*)\nFROM table_name\nGROUP BY column1;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6bcf\u500b\u4e0d\u91cd\u8907\u7684 column1<\/code> \u503c\u53ca\u5176\u51fa\u73fe\u7684\u6b21\u6578\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT city, COUNT(*)\nFROM customers\nGROUP BY city;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6bcf\u500b\u57ce\u5e02\u53ca\u5176\u5c0d\u61c9\u7684\u5ba2\u6236\u6578\u91cf\u3002<\/p>\n
\u53bb\u9664\u91cd\u8907\u6578\u64da\u7684\u5176\u4ed6\u65b9\u6cd5<\/h2>\n
\u9664\u4e86\u4f7f\u7528 SELECT DISTINCT<\/code> \u548c GROUP BY<\/code>\uff0c\u9084\u53ef\u4ee5\u4f7f\u7528\u5176\u4ed6\u65b9\u6cd5\u4f86\u53bb\u9664\u91cd\u8907\u6578\u64da\u3002\u4f8b\u5982\uff0c\u53ef\u4ee5\u4f7f\u7528 ROW_NUMBER()<\/code> \u51fd\u6578\u4f86\u70ba\u6bcf\u4e00\u884c\u5206\u914d\u4e00\u500b\u552f\u4e00\u7684\u5e8f\u865f\uff0c\u7136\u5f8c\u9078\u64c7\u5e8f\u865f\u70ba 1 \u7684\u884c\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff1a<\/p>\n
WITH CTE AS (\n    SELECT *,\n           ROW_NUMBER() OVER (PARTITION BY column1 ORDER BY (SELECT NULL)) AS rn\n    FROM table_name\n)\nSELECT *\nFROM CTE\nWHERE rn = 1;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6bcf\u500b column1<\/code> \u7684\u7b2c\u4e00\u884c\uff0c\u5f9e\u800c\u53bb\u9664\u91cd\u8907\u6578\u64da\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u67e5\u8a62\u4e00\u5f35\u8868\u4e2d\u7684\u4e0d\u91cd\u8907\u6578\u64da\u662f\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\u7684\u4e00\u500b\u57fa\u672c\u64cd\u4f5c\u3002\u901a\u904e\u4f7f\u7528 SELECT DISTINCT<\/code>\u3001GROUP BY<\/code> \u548c\u5176\u4ed6\u65b9\u6cd5\uff0c\u60a8\u53ef\u4ee5\u6709\u6548\u5730\u8b58\u5225\u548c\u53bb\u9664\u91cd\u8907\u6578\u64da\uff0c\u5f9e\u800c\u63d0\u9ad8\u6578\u64da\u7684\u6e96\u78ba\u6027\u548c\u53ef\u9760\u6027\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u4f01\u696d\u4f86\u8aaa\uff0c\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\u81f3\u95dc\u91cd\u8981\u3002\u82e5\u60a8\u5c0d\u65bc \u9999\u6e2fVPS<\/a> \u6216\u5176\u4ed6\u6578\u64da\u5eab\u7ba1\u7406\u89e3\u6c7a\u65b9\u6848\u611f\u8208\u8da3\uff0c\u8acb\u96a8\u6642\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u8cc7\u8a0a\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5b78\u7fd2\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u67e5\u8a62\u4e00\u5f35\u8868\u7684\u7368\u7279\u6578\u64da\uff0c\u8f15\u9b06\u53bb\u9664\u91cd\u8907\u9805\uff0c\u63d0\u5347\u6578\u64da\u5206\u6790\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-172833","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/172833","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=172833"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/172833\/revisions"}],"predecessor-version":[{"id":172834,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/172833\/revisions\/172834"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=172833"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=172833"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=172833"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}