{"id":200532,"date":"2025-05-06T08:01:49","date_gmt":"2025-05-06T00:01:49","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200532\/"},"modified":"2025-05-06T08:01:49","modified_gmt":"2025-05-06T00:01:49","slug":"%e5%a4%a7%e6%95%b0%e6%8d%ae%e9%87%8f%e4%b8%8b%ef%bc%8c%e5%a6%82%e4%bd%95%e9%ab%98%e6%95%88%e6%9f%a5%e8%af%a2%e5%b0%8f%e4%ba%8e%e7%ad%89%e4%ba%8e%e6%9f%90%e4%b8%aa%e5%80%bc%e7%9a%84%e6%9c%88%e4%bb%bd","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200532\/","title":{"rendered":"\u5927\u6570\u636e\u91cf\u4e0b\uff0c\u5982\u4f55\u9ad8\u6548\u67e5\u8be2\u5c0f\u4e8e\u7b49\u4e8e\u67d0\u4e2a\u503c\u7684\u6708\u4efd\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u5927\u6570\u636e\u91cf\u4e0b\uff0c\u5982\u4f55\u9ad8\u6548\u67e5\u8be2\u5c0f\u4e8e\u7b49\u4e8e\u67d0\u4e2a\u503c\u7684\u6708\u4efd\uff1f <\/h1>\n<p>\u5b66\u4e60\u8981\u52aa\u529b\uff0c\u4f46\u662f\u4e0d\u8981\u6025\uff01\u4eca\u5929\u7684\u8fd9\u7bc7\u6587\u7ae0\u5c06\u4f1a\u4ecb\u7ecd\u5230\u7b49\u7b49\u77e5\u8bc6\u70b9\uff0c\u5982\u679c\u4f60\u60f3\u6df1\u5165\u5b66\u4e60\uff0c\u53ef\u4ee5\u5173\u6ce8\u6211\uff01\u6211\u4f1a\u6301\u7eed\u66f4\u65b0\u76f8\u5173\u6587\u7ae0\u7684\uff0c\u5e0c\u671b\u5bf9\u5927\u5bb6\u90fd\u80fd\u6709\u6240\u5e2e\u52a9\uff01<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241107\/1730984620672cbaace0626.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>mysql \u8bbe\u8ba1\u57fa\u7840\uff1a\u6570\u636e\u91cf\u5927\u65f6\u7684\u67e5\u8be2\u4f18\u5316<\/strong><\/p>\n<p>\u672c\u6587\u63a2\u8ba8\u4e86\u4e24\u79cd\u67e5\u8be2\u65b9\u6cd5\uff0c\u7528\u4e8e\u4ece\u8868 newtable \u4e2d\u67e5\u8be2\u5c0f\u4e8e\u7b49\u4e8e\u7ed9\u5b9a\u503c\u7684\u6708\u4efd\u3002<\/p>\n<p><strong>\u65b9\u6cd5 1\uff1a<\/strong><\/p>\n<pre>select max(month) from newtabel where month&lt;=9<\/pre>\n<p><strong>\u65b9\u6cd5 2\uff1a<\/strong><\/p>\n<pre>select month from newtabel where month&lt;=9 order by month desc limit 1<\/pre>\n<p>\u5f53\u6570\u636e\u91cf\u8f83\u5c0f\u65f6\uff0c\u8fd9\u4e24\u79cd\u65b9\u6cd5\u7684\u6027\u80fd\u5dee\u522b\u5e76\u4e0d\u660e\u663e\u3002\u7136\u800c\uff0c\u5728\u5927\u6570\u636e\u91cf\u60c5\u51b5\u4e0b\uff0c\u65b9\u6cd5 2 \u66f4\u4e3a\u9ad8\u6548\u3002<\/p>\n<p><strong>\u539f\u56e0\uff1a<\/strong><\/p>\n<ul>\n<li>\u65b9\u6cd5 1 \u9700\u8981\u5bf9\u8868\u8fdb\u884c\u4e00\u6b21\u5168\u8868\u626b\u63cf\uff0c\u8fd9\u5bf9\u4e8e\u5927\u6570\u636e\u91cf\u8868\u6765\u8bf4\u53ef\u80fd\u662f\u8017\u65f6\u7684\u3002<\/li>\n<li>\u65b9\u6cd5 2 \u4f7f\u7528\u4e86\u7d22\u5f15\uff0c\u5b83\u53ef\u4ee5\u76f4\u63a5\u5b9a\u4f4d\u5230\u6ee1\u8db3\u6761\u4ef6\u7684\u884c\uff0c\u4ece\u800c\u663e\u7740\u63d0\u9ad8\u67e5\u8be2\u901f\u5ea6\u3002<\/li>\n<\/ul>\n<p><strong>\u66f4\u597d\u7684\u5199\u6cd5\uff1a<\/strong><\/p>\n<p>\u4e3a\u4e86\u83b7\u5f97\u66f4\u597d\u7684\u6027\u80fd\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u66f4\u597d\u7684\u5199\u6cd5\uff1a<\/p>\n<pre>SELECT month FROM NewTable WHERE month &lt;= 9 AND month = (SELECT MAX(month) FROM NewTable WHERE month &lt;= 9)<\/pre>\n<p><strong>mysql \u6d4b\u8bd5\u548c\u5206\u6790\u5de5\u5177\uff1a<\/strong><\/p>\n<ul>\n<li><strong>explain\uff1a<\/strong>\u7528\u4e8e\u5206\u6790 sql \u67e5\u8be2\u7684\u6267\u884c\u8ba1\u5212\uff0c\u5e2e\u52a9\u4f60\u4e86\u89e3\u67e5\u8be2\u5982\u4f55\u4f7f\u7528\u7d22\u5f15\u548c\u8868\u3002<\/li>\n<li><strong>\u5b58\u50a8\u8fc7\u7a0b\uff1a<\/strong>\u7528\u4e8e\u521b\u5efa\u53ef\u91cd\u7528\u7684 sql \u4ee3\u7801\u5757\uff0c\u8fd9\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u548c\u53ef\u7ef4\u62a4\u6027\u3002<\/li>\n<li><strong>mysqltuner\uff1a<\/strong>\u4e00\u4e2a\u5f00\u6e90\u5de5\u5177\uff0c\u53ef\u4ee5\u5206\u6790 mysql \u670d\u52a1\u5668\u5e76\u63d0\u4f9b\u6027\u80fd\u4f18\u5316\u5efa\u8bae\u3002<\/li>\n<\/ul>\n<p>\u597d\u4e86\uff0c\u672c\u6587\u5230\u6b64\u7ed3\u675f\uff0c\u5e26\u5927\u5bb6\u4e86\u89e3\u4e86\u300a\u5927\u6570\u636e\u91cf\u4e0b\uff0c\u5982\u4f55\u9ad8\u6548\u67e5\u8be2\u5c0f\u4e8e\u7b49\u4e8e\u67d0\u4e2a\u503c\u7684\u6708\u4efd\uff1f \u300b\uff0c\u5e0c\u671b\u672c\u6587\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\uff01\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff0c\u7ed9\u5927\u5bb6\u5206\u4eab\u66f4\u591a\u6570\u636e\u5e93\u77e5\u8bc6\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>\u5927\u6570\u636e\u91cf\u4e0b\uff0c\u5982\u4f55\u9ad8\u6548\u67e5\u8be2\u5c0f\u4e8e\u7b49\u4e8e&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-200532","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200532","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=200532"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200532\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200532"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200532"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200532"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}