{"id":158167,"date":"2024-11-03T00:33:37","date_gmt":"2024-11-02T16:33:37","guid":{"rendered":"https:\/\/server.hk\/cnblog\/158167\/"},"modified":"2024-11-03T00:33:38","modified_gmt":"2024-11-02T16:33:38","slug":"%e9%ab%98%e6%95%88%e7%b2%be%e6%ba%96%e7%9a%84%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9f%a5%e8%a9%a2%ef%bc%8c%e8%bc%95%e9%ac%86%e7%b5%b1%e8%a8%88%e6%95%b8%e6%93%9a%e6%95%b8%e9%87%8f%ef%bc%88%e6%95%b8%e6%93%9a","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/158167\/","title":{"rendered":"\u9ad8\u6548\u7cbe\u6e96\u7684\u6578\u64da\u5eab\u67e5\u8a62\uff0c\u8f15\u9b06\u7d71\u8a08\u6578\u64da\u6578\u91cf\uff08\u6578\u64da\u5eab\u67e5\u8a62 \u7d71\u8a08\u6578\u91cf\uff09"},"content":{"rendered":"<h1 id=\"%e9%ab%98%e6%95%88%e7%b2%be%e6%ba%96%e7%9a%84%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9f%a5%e8%a9%a2%ef%bc%8c%e8%bc%95%e9%ac%86%e7%b5%b1%e8%a8%88%e6%95%b8%e6%93%9a%e6%95%b8%e9%87%8f-NXpfYMjLKf\">\u9ad8\u6548\u7cbe\u6e96\u7684\u6578\u64da\u5eab\u67e5\u8a62\uff0c\u8f15\u9b06\u7d71\u8a08\u6578\u64da\u6578\u91cf<\/h1>\n<p>\u5728\u7576\u4eca\u6578\u64da\u9a45\u52d5\u7684\u4e16\u754c\u4e2d\uff0c\u6578\u64da\u5eab\u67e5\u8a62\u7684\u6548\u7387\u548c\u6e96\u78ba\u6027\u5c0d\u65bc\u4f01\u696d\u7684\u6210\u529f\u81f3\u95dc\u91cd\u8981\u3002\u7121\u8ad6\u662f\u9032\u884c\u696d\u52d9\u5206\u6790\u3001\u7528\u6236\u884c\u70ba\u7814\u7a76\uff0c\u9084\u662f\u7c21\u55ae\u7684\u6578\u64da\u7d71\u8a08\uff0c\u638c\u63e1\u9ad8\u6548\u7684\u6578\u64da\u5eab\u67e5\u8a62\u6280\u8853\u90fd\u662f\u5fc5\u4e0d\u53ef\u5c11\u7684\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u9032\u884c\u9ad8\u6548\u7684\u6578\u64da\u5eab\u67e5\u8a62\uff0c\u4e26\u8f15\u9b06\u7d71\u8a08\u6578\u64da\u6578\u91cf\u3002<\/p>\n<h2 id=\"%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9f%a5%e8%a9%a2%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-NXpfYMjLKf\">\u6578\u64da\u5eab\u67e5\u8a62\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p>\u6578\u64da\u5eab\u67e5\u8a62\u662f\u6307\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u6578\u64da\u7684\u904e\u7a0b\u3002\u9019\u4e00\u904e\u7a0b\u901a\u5e38\u4f7f\u7528\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff08SQL\uff09\u4f86\u5be6\u73fe\u3002SQL\u662f\u4e00\u7a2e\u6a19\u6e96\u7684\u6578\u64da\u5eab\u67e5\u8a62\u8a9e\u8a00\uff0c\u80fd\u5920\u8b93\u7528\u6236\u4ee5\u7c21\u55ae\u7684\u8a9e\u6cd5\u4f86\u9032\u884c\u6578\u64da\u7684\u589e\u3001\u522a\u3001\u6539\u3001\u67e5\u7b49\u64cd\u4f5c\u3002<\/p>\n<h2 id=\"%e9%ab%98%e6%95%88%e6%9f%a5%e8%a9%a2%e7%9a%84%e9%97%9c%e9%8d%b5%e8%a6%81%e7%b4%a0-NXpfYMjLKf\">\u9ad8\u6548\u67e5\u8a62\u7684\u95dc\u9375\u8981\u7d20<\/h2>\n<p>\u8981\u5be6\u73fe\u9ad8\u6548\u7684\u6578\u64da\u5eab\u67e5\u8a62\uff0c\u4ee5\u4e0b\u5e7e\u500b\u8981\u7d20\u662f\u4e0d\u53ef\u5ffd\u8996\u7684\uff1a<\/p>\n<ul>\n<li><strong>\u7d22\u5f15\u7684\u4f7f\u7528\uff1a<\/strong>\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\u3002\u901a\u904e\u5728\u8868\u7684\u67d0\u4e9b\u5217\u4e0a\u5275\u5efa\u7d22\u5f15\uff0c\u6578\u64da\u5eab\u53ef\u4ee5\u66f4\u5feb\u5730\u5b9a\u4f4d\u5230\u6240\u9700\u7684\u6578\u64da\u3002<\/li>\n<li><strong>\u67e5\u8a62\u512a\u5316\uff1a<\/strong>\u7de8\u5beb\u9ad8\u6548\u7684SQL\u67e5\u8a62\u8a9e\u53e5\u662f\u95dc\u9375\u3002\u907f\u514d\u4f7f\u7528\u4e0d\u5fc5\u8981\u7684\u5b50\u67e5\u8a62\uff0c\u4e26\u76e1\u91cf\u6e1b\u5c11\u8fd4\u56de\u7684\u6578\u64da\u91cf\u3002<\/li>\n<li><strong>\u6578\u64da\u5eab\u8a2d\u8a08\uff1a<\/strong>\u826f\u597d\u7684\u6578\u64da\u5eab\u8a2d\u8a08\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002\u6b63\u898f\u5316\u548c\u53cd\u6b63\u898f\u5316\u7684\u5e73\u8861\u662f\u8a2d\u8a08\u4e2d\u7684\u91cd\u8981\u8003\u91cf\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%b1%e8%a8%88%e6%95%b8%e6%93%9a%e6%95%b8%e9%87%8f%e7%9a%84%e5%b8%b8%e7%94%a8%e6%96%b9%e6%b3%95-NXpfYMjLKf\">\u7d71\u8a08\u6578\u64da\u6578\u91cf\u7684\u5e38\u7528\u65b9\u6cd5<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u4e2d\u7d71\u8a08\u6578\u64da\u6578\u91cf\u901a\u5e38\u4f7f\u7528SQL\u4e2d\u7684\u805a\u5408\u51fd\u6578\uff0c\u6700\u5e38\u7528\u7684\u5c31\u662fCOUNT()\u51fd\u6578\u3002\u9019\u500b\u51fd\u6578\u53ef\u4ee5\u7528\u4f86\u8a08\u7b97\u8868\u4e2d\u7b26\u5408\u7279\u5b9a\u689d\u4ef6\u7684\u884c\u6578\u3002<\/p>\n<h3 id=\"%e4%bd%bf%e7%94%a8count%e5%87%bd%e6%95%b8%e7%9a%84%e7%af%84%e4%be%8b-NXpfYMjLKf\">\u4f7f\u7528COUNT()\u51fd\u6578\u7684\u7bc4\u4f8b<\/h3>\n<pre><code>SELECT COUNT(*) FROM users WHERE status = 'active';<\/code><\/pre>\n<p>\u4e0a\u8ff0\u67e5\u8a62\u5c07\u8fd4\u56de\u201cusers\u201d\u8868\u4e2d\u6240\u6709\u72c0\u614b\u70ba\u201cactive\u201d\u7684\u7528\u6236\u6578\u91cf\u3002\u9019\u662f\u4e00\u500b\u7c21\u55ae\u800c\u6709\u6548\u7684\u67e5\u8a62\u65b9\u5f0f\u3002<\/p>\n<h3 id=\"%e7%b5%90%e5%90%88group-by%e9%80%b2%e8%a1%8c%e5%88%86%e7%b5%84%e7%b5%b1%e8%a8%88-NXpfYMjLKf\">\u7d50\u5408GROUP BY\u9032\u884c\u5206\u7d44\u7d71\u8a08<\/h3>\n<p>\u5982\u679c\u9700\u8981\u5c0d\u6578\u64da\u9032\u884c\u5206\u7d44\u7d71\u8a08\uff0c\u53ef\u4ee5\u4f7f\u7528GROUP BY\u8a9e\u53e5\u3002\u9019\u6a23\u53ef\u4ee5\u6839\u64da\u67d0\u4e00\u5217\u7684\u503c\u4f86\u7d71\u8a08\u6578\u91cf\u3002<\/p>\n<pre><code>SELECT country, COUNT(*) FROM users GROUP BY country;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u500b\u570b\u5bb6\u7684\u7528\u6236\u6578\u91cf\uff0c\u5e6b\u52a9\u4f01\u696d\u4e86\u89e3\u5176\u7528\u6236\u7684\u5730\u7406\u5206\u4f48\u3002<\/p>\n<h2 id=\"%e6%9f%a5%e8%a9%a2%e6%80%a7%e8%83%bd%e7%9a%84%e6%8f%90%e5%8d%87%e6%8a%80%e5%b7%a7-NXpfYMjLKf\">\u67e5\u8a62\u6027\u80fd\u7684\u63d0\u5347\u6280\u5de7<\/h2>\n<p>\u9664\u4e86\u57fa\u672c\u7684\u67e5\u8a62\u512a\u5316\uff0c\u9084\u6709\u4e00\u4e9b\u9032\u968e\u6280\u5de7\u53ef\u4ee5\u9032\u4e00\u6b65\u63d0\u5347\u67e5\u8a62\u6027\u80fd\uff1a<\/p>\n<ul>\n<li><strong>\u4f7f\u7528EXPLAIN\u5206\u6790\u67e5\u8a62\u8a08\u5283\uff1a<\/strong>\u901a\u904eEXPLAIN\u8a9e\u53e5\uff0c\u53ef\u4ee5\u67e5\u770b\u6578\u64da\u5eab\u5982\u4f55\u57f7\u884c\u67e5\u8a62\uff0c\u5f9e\u800c\u627e\u51fa\u6027\u80fd\u74f6\u9838\u3002<\/li>\n<li><strong>\u907f\u514dSELECT *\uff1a<\/strong>\u5728\u67e5\u8a62\u6642\uff0c\u76e1\u91cf\u6307\u5b9a\u9700\u8981\u7684\u5217\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u6578\u64da\u50b3\u8f38\u91cf\uff0c\u63d0\u9ad8\u6548\u7387\u3002<\/li>\n<li><strong>\u5b9a\u671f\u7dad\u8b77\u6578\u64da\u5eab\uff1a<\/strong>\u5b9a\u671f\u9032\u884c\u6578\u64da\u5eab\u7684\u6e05\u7406\u548c\u91cd\u5efa\u7d22\u5f15\uff0c\u53ef\u4ee5\u4fdd\u6301\u6578\u64da\u5eab\u7684\u9ad8\u6548\u904b\u884c\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-NXpfYMjLKf\">\u7e3d\u7d50<\/h2>\n<p>\u9ad8\u6548\u7cbe\u6e96\u7684\u6578\u64da\u5eab\u67e5\u8a62\u4e0d\u50c5\u80fd\u63d0\u9ad8\u6578\u64da\u6aa2\u7d22\u7684\u901f\u5ea6\uff0c\u9084\u80fd\u5e6b\u52a9\u4f01\u696d\u66f4\u597d\u5730\u9032\u884c\u6578\u64da\u5206\u6790\u548c\u6c7a\u7b56\u3002\u901a\u904e\u5408\u7406\u4f7f\u7528\u7d22\u5f15\u3001\u512a\u5316\u67e5\u8a62\u8a9e\u53e5\u4ee5\u53ca\u5b9a\u671f\u7dad\u8b77\u6578\u64da\u5eab\uff0c\u4f01\u696d\u53ef\u4ee5\u5728\u6fc0\u70c8\u7684\u5e02\u5834\u7af6\u722d\u4e2d\u4fdd\u6301\u512a\u52e2\u3002\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u53ef\u9760\u7684 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0c\u4ee5\u652f\u6301\u60a8\u7684\u6578\u64da\u5eab\u9700\u6c42\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u52a9\u60a8\u8f15\u9b06\u7ba1\u7406\u548c\u5206\u6790\u6578\u64da\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u9ad8\u6548\u7cbe\u6e96\u7684\u6578\u64da\u5eab\u67e5\u8a62\u5de5\u5177\uff0c\u8f15\u9b06\u7d71\u8a08\u6578\u64da\u6578\u91cf\uff0c\u63d0\u5347\u6578\u64da\u5206\u6790\u6548\u7387\uff0c\u52a9\u60a8\u5feb\u901f\u7372\u53d6\u6240\u9700\u8cc7\u8a0a\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-158167","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/158167","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=158167"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/158167\/revisions"}],"predecessor-version":[{"id":158168,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/158167\/revisions\/158168"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=158167"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=158167"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=158167"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}