{"id":5290,"date":"2024-11-14T08:41:18","date_gmt":"2024-11-14T00:41:18","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5290\/"},"modified":"2024-11-14T08:41:18","modified_gmt":"2024-11-14T00:41:18","slug":"mysql%e5%b0%8f%e4%ba%8e%e7%ad%89%e4%ba%8e%e6%80%8e%e4%b9%88%e5%86%99","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5290\/","title":{"rendered":"mysql\u5c0f\u4e8e\u7b49\u4e8e\u600e\u4e48\u5199"},"content":{"rendered":"<blockquote><p>\n  mysql \u4e2d\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26 (\n<\/p><\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/202405\/26\/2024052618305222293.jpg\" class=\"aligncenter\" title=\"mysql\u5c0f\u4e8e\u7b49\u4e8e\u600e\u4e48\u5199\u63d2\u56fe\" alt=\"mysql\u5c0f\u4e8e\u7b49\u4e8e\u600e\u4e48\u5199\u63d2\u56fe\" \/><\/p>\n<p><strong>MySQL \u4e2d\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26<\/strong><\/p>\n<p><strong>\u8fd0\u7b97\u7b26\uff1a<\/strong> <\/p>\n<p><strong>\u63cf\u8ff0\uff1a<\/strong><\/p>\n<p>\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u7528\u4e8e\u6bd4\u8f83\u4e24\u4e2a\u503c\uff0c\u5982\u679c\u7b2c\u4e00\u4e2a\u503c\u5c0f\u4e8e\u6216\u7b49\u4e8e\u7b2c\u4e8c\u4e2a\u503c\uff0c\u5219\u8fd4\u56de true\u3002<\/p>\n<p><strong>\u8bed\u6cd5\uff1a<\/strong><\/p>\n<pre>express1 &lt;= express2<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p>\u5176\u4e2d\uff0cexpress1 \u548c express2 \u662f\u8981\u6bd4\u8f83\u7684\u503c\u3002<\/p>\n<p><strong>\u793a\u4f8b\uff1a<\/strong><\/p>\n<pre>SELECT * FROM users WHERE age &lt;= 25;<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p>\u8be5\u67e5\u8be2\u5c06\u9009\u62e9\u6240\u6709\u5e74\u9f84\u5c0f\u4e8e\u6216\u7b49\u4e8e 25 \u5c81\u7684\u7528\u6237\u3002<\/p>\n<p><strong>\u5176\u4ed6\u6ce8\u610f\u4e8b\u9879\uff1a<\/strong><\/p>\n<ul>\n<li>\u5bf9\u4e8e\u5b57\u7b26\u4e32\uff0c\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u57fa\u4e8e\u5b57\u6bcd\u987a\u5e8f\u8fdb\u884c\u6bd4\u8f83\u3002<\/li>\n<li>\u5bf9\u4e8e\u65e5\u671f\u548c\u65f6\u95f4\uff0c\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u57fa\u4e8e\u65f6\u95f4\u987a\u5e8f\u8fdb\u884c\u6bd4\u8f83\u3002<\/li>\n<li>\n<p>\u5bf9\u4e8e NULL \u503c\uff0c\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u7684\u884c\u4e3a\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>NULL <\/li>\n<li>NULL <\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>\u4ee5\u4e0a\u5c31\u662f\u5c0f\u4e8e\u7b49\u4e8e\u600e\u4e48\u5199\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>mysql \u4e2d\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26 ( MySQL \u4e2d\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26 \u8fd0\u7b97\u7b26\uff1a \u63cf\u8ff0\uff1a \u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u7528\u4e8e\u6bd4\u8f83\u4e24\u4e2a\u503c\uff0c\u5982\u679c\u7b2c\u4e00\u4e2a\u503c\u5c0f\u4e8e\u6216\u7b49\u4e8e\u7b2c\u4e8c\u4e2a\u503c\uff0c\u5219\u8fd4\u56de true\u3002 \u8bed\u6cd5\uff1a express1 &lt;= express2 \u767b\u5f55\u540e\u590d\u5236 \u5176\u4e2d\uff0cexpress1 \u548c express2 \u662f\u8981\u6bd4\u8f83\u7684\u503c\u3002 \u793a\u4f8b\uff1a SELECT * FROM users WHERE age &lt;= 25; \u767b\u5f55\u540e\u590d\u5236 \u8be5\u67e5\u8be2\u5c06\u9009\u62e9\u6240\u6709\u5e74\u9f84\u5c0f\u4e8e\u6216\u7b49\u4e8e 25 \u5c81\u7684\u7528\u6237\u3002 \u5176\u4ed6\u6ce8\u610f\u4e8b\u9879\uff1a \u5bf9\u4e8e\u5b57\u7b26\u4e32\uff0c\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u57fa\u4e8e\u5b57\u6bcd\u987a\u5e8f\u8fdb\u884c\u6bd4\u8f83\u3002 \u5bf9\u4e8e\u65e5\u671f\u548c\u65f6\u95f4\uff0c\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u57fa\u4e8e\u65f6\u95f4\u987a\u5e8f\u8fdb\u884c\u6bd4\u8f83\u3002 \u5bf9\u4e8e NULL \u503c\uff0c\u5c0f\u4e8e\u7b49\u4e8e\u8fd0\u7b97\u7b26\u7684\u884c\u4e3a\u5982\u4e0b\uff1a NULL NULL \u4ee5\u4e0a\u5c31\u662f\u5c0f\u4e8e\u7b49\u4e8e\u600e\u4e48\u5199\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-5290","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5290","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=5290"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5290\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5290"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5290"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5290"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}