{"id":194779,"date":"2024-11-13T09:30:17","date_gmt":"2024-11-13T01:30:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/194779\/"},"modified":"2024-11-13T09:30:18","modified_gmt":"2024-11-13T01:30:18","slug":"%e5%90%ab%e6%9c%89group-by%e5%ad%90%e5%8f%a5%e7%9a%84%e6%9f%a5%e8%a9%a2%e4%b8%ad%e5%a6%82%e4%bd%95%e9%a1%af%e7%a4%bacount%e7%82%ba0%e7%9a%84%e7%b5%90%e6%9e%9c","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/194779\/","title":{"rendered":"\u542b\u6709GROUP BY\u5b50\u53e5\u7684\u67e5\u8a62\u4e2d\u5982\u4f55\u986f\u793aCOUNT()\u70ba0\u7684\u7d50\u679c"},"content":{"rendered":"<h1 id=\"%e5%90%ab%e6%9c%89group-by%e5%ad%90%e5%8f%a5%e7%9a%84%e6%9f%a5%e8%a9%a2%e4%b8%ad%e5%a6%82%e4%bd%95%e9%a1%af%e7%a4%bacount%e7%82%ba0%e7%9a%84%e7%b5%90%e6%9e%9c-chJjdMozIb\">\u542b\u6709GROUP BY\u5b50\u53e5\u7684\u67e5\u8a62\u4e2d\u5982\u4f55\u986f\u793aCOUNT()\u70ba0\u7684\u7d50\u679c<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u67e5\u8a62\u4e2d\uff0c\u4f7f\u7528 <code>GROUP BY<\/code> \u5b50\u53e5\u53ef\u4ee5\u5c07\u7d50\u679c\u96c6\u6309\u7279\u5b9a\u5217\u9032\u884c\u5206\u7d44\uff0c\u4e26\u4e14\u901a\u5e38\u6703\u8207\u805a\u5408\u51fd\u6578\u5982 <code>COUNT()<\/code> \u4e00\u8d77\u4f7f\u7528\uff0c\u4ee5\u8a08\u7b97\u6bcf\u500b\u7d44\u7684\u8a18\u9304\u6578\u3002\u7136\u800c\uff0c\u7576\u67d0\u4e9b\u7d44\u6c92\u6709\u4efb\u4f55\u8a18\u9304\u6642\uff0c\u9ed8\u8a8d\u60c5\u6cc1\u4e0b\u9019\u4e9b\u7d44\u4e0d\u6703\u51fa\u73fe\u5728\u67e5\u8a62\u7d50\u679c\u4e2d\u3002\u9019\u4f7f\u5f97\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6211\u5011\u9700\u8981\u986f\u793a <code>COUNT()<\/code> \u70ba0\u7684\u7d50\u679c\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u5728\u542b\u6709 <code>GROUP BY<\/code> \u5b50\u53e5\u7684\u67e5\u8a62\u4e2d\u5be6\u73fe\u9019\u4e00\u76ee\u6a19\u3002<\/p>\n<h2 id=\"%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-chJjdMozIb\">\u57fa\u672c\u6982\u5ff5<\/h2>\n<p>\u5728 SQL \u4e2d\uff0c<code>GROUP BY<\/code> \u5b50\u53e5\u7528\u65bc\u5c07\u7d50\u679c\u96c6\u4e2d\u7684\u884c\u5206\u7d44\uff0c\u4e26\u4e14\u53ef\u4ee5\u8207\u805a\u5408\u51fd\u6578\u4e00\u8d77\u4f7f\u7528\u4f86\u8a08\u7b97\u6bcf\u500b\u7d44\u7684\u7d71\u8a08\u6578\u64da\u3002\u4f8b\u5982\uff0c\u4ee5\u4e0b\u67e5\u8a62\u5c07\u6309\u985e\u5225\u5206\u7d44\u4e26\u8a08\u7b97\u6bcf\u500b\u985e\u5225\u7684\u7522\u54c1\u6578\u91cf\uff1a<\/p>\n<pre><code>SELECT category, COUNT(*) as product_count\nFROM products\nGROUP BY category;<\/code><\/pre>\n<p>\u5982\u679c\u67d0\u4e9b\u985e\u5225\u6c92\u6709\u4efb\u4f55\u7522\u54c1\uff0c\u5247\u9019\u4e9b\u985e\u5225\u5c07\u4e0d\u6703\u51fa\u73fe\u5728\u7d50\u679c\u4e2d\u3002\u70ba\u4e86\u89e3\u6c7a\u9019\u500b\u554f\u984c\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u5de6\u9023\u63a5\uff08LEFT JOIN\uff09\u4f86\u78ba\u4fdd\u6240\u6709\u985e\u5225\u90fd\u986f\u793a\u5728\u7d50\u679c\u4e2d\uff0c\u5373\u4f7f\u5b83\u5011\u7684\u8a08\u6578\u70ba0\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e5%b7%a6%e9%80%a3%e6%8e%a5%e9%a1%af%e7%a4%ba0%e8%a8%88%e6%95%b8-chJjdMozIb\">\u4f7f\u7528\u5de6\u9023\u63a5\u986f\u793a0\u8a08\u6578<\/h2>\n<p>\u70ba\u4e86\u986f\u793a\u6240\u6709\u985e\u5225\uff0c\u5373\u4f7f\u5b83\u5011\u7684\u8a08\u6578\u70ba0\uff0c\u6211\u5011\u53ef\u4ee5\u5c07\u985e\u5225\u8868\u8207\u7522\u54c1\u8868\u9032\u884c\u5de6\u9023\u63a5\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT c.category_name, COUNT(p.product_id) as product_count\nFROM categories c\nLEFT JOIN products p ON c.category_id = p.category_id\nGROUP BY c.category_name;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u9996\u5148\u9078\u64c7\u4e86\u985e\u5225\u8868\u4e2d\u7684\u6240\u6709\u985e\u5225\uff0c\u7136\u5f8c\u4f7f\u7528\u5de6\u9023\u63a5\u5c07\u5176\u8207\u7522\u54c1\u8868\u9023\u63a5\u3002\u9019\u6a23\uff0c\u5373\u4f7f\u67d0\u4e9b\u985e\u5225\u6c92\u6709\u7522\u54c1\uff0c\u9019\u4e9b\u985e\u5225\u4ecd\u7136\u6703\u51fa\u73fe\u5728\u7d50\u679c\u4e2d\uff0c\u4e26\u4e14 <code>COUNT()<\/code> \u5c07\u986f\u793a\u70ba0\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e5%ad%90%e6%9f%a5%e8%a9%a2%e9%a1%af%e7%a4%ba0%e8%a8%88%e6%95%b8-chJjdMozIb\">\u4f7f\u7528\u5b50\u67e5\u8a62\u986f\u793a0\u8a08\u6578<\/h2>\n<p>\u53e6\u4e00\u7a2e\u65b9\u6cd5\u662f\u4f7f\u7528\u5b50\u67e5\u8a62\u4f86\u7372\u53d6\u6240\u6709\u985e\u5225\uff0c\u7136\u5f8c\u5728\u5916\u90e8\u67e5\u8a62\u4e2d\u9032\u884c\u8a08\u6578\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT c.category_name, \n       (SELECT COUNT(*) \n        FROM products p \n        WHERE p.category_id = c.category_id) as product_count\nFROM categories c;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u5c0d\u6bcf\u500b\u985e\u5225\u57f7\u884c\u4e86\u4e00\u500b\u5b50\u67e5\u8a62\uff0c\u4ee5\u8a08\u7b97\u8a72\u985e\u5225\u7684\u7522\u54c1\u6578\u91cf\u3002\u9019\u6a23\uff0c\u5373\u4f7f\u67d0\u500b\u985e\u5225\u6c92\u6709\u7522\u54c1\uff0c\u5916\u90e8\u67e5\u8a62\u4ecd\u7136\u6703\u8fd4\u56de\u8a72\u985e\u5225\uff0c\u4e26\u4e14\u8a08\u6578\u70ba0\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-chJjdMozIb\">\u7d50\u8ad6<\/h2>\n<p>\u5728 SQL \u67e5\u8a62\u4e2d\uff0c\u7576\u4f7f\u7528 <code>GROUP BY<\/code> \u5b50\u53e5\u6642\uff0c\u9ed8\u8a8d\u60c5\u6cc1\u4e0b\u4e0d\u6703\u986f\u793a\u8a08\u6578\u70ba0\u7684\u7d50\u679c\u3002\u901a\u904e\u4f7f\u7528\u5de6\u9023\u63a5\u6216\u5b50\u67e5\u8a62\uff0c\u6211\u5011\u53ef\u4ee5\u78ba\u4fdd\u6240\u6709\u7d44\u90fd\u986f\u793a\u5728\u7d50\u679c\u4e2d\uff0c\u7121\u8ad6\u5b83\u5011\u7684\u8a08\u6578\u5982\u4f55\u3002\u9019\u5c0d\u65bc\u9700\u8981\u5b8c\u6574\u6578\u64da\u8996\u5716\u7684\u5831\u544a\u548c\u5206\u6790\u7279\u5225\u91cd\u8981\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\u4ee5\u6eff\u8db3\u60a8\u7684\u9700\u6c42\u3002\u6211\u5011\u7684 <a href=\"https:\/\/server.hk\">\u4e91\u670d\u52a1\u5668<\/a> \u670d\u52d9\u80fd\u5920\u652f\u6301\u5404\u7a2e\u61c9\u7528\u7a0b\u5e8f\uff0c\u4e26\u78ba\u4fdd\u60a8\u7684\u6578\u64da\u5b89\u5168\u548c\u53ef\u9760\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3\u5982\u4f55\u5728\u542b\u6709GROUP BY\u5b50\u53e5\u7684\u67e5\u8a62\u4e2d\u986f\u793aCOUNT()\u70ba0\u7684\u7d50\u679c\uff0c\u78ba\u4fdd\u6240\u6709\u5206\u7d44\u90fd\u88ab\u6b63\u78ba\u986f\u793a\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-194779","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/194779","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=194779"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/194779\/revisions"}],"predecessor-version":[{"id":194780,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/194779\/revisions\/194780"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=194779"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=194779"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=194779"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}