{"id":154411,"date":"2024-11-02T15:35:18","date_gmt":"2024-11-02T07:35:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/154411\/"},"modified":"2024-11-02T15:35:19","modified_gmt":"2024-11-02T07:35:19","slug":"%e9%83%bd%e6%98%af%e5%90%8c%e6%a8%a3%e6%a2%9d%e4%bb%b6%e7%9a%84-mysql-select-%e8%aa%9e%e5%8f%a5%ef%bc%8c%e7%82%ba%e4%bd%95%e8%ae%80%e5%88%b0%e7%9a%84%e5%85%a7%e5%ae%b9%e5%8d%bb%e4%b8%8d%e4%b8%80","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/154411\/","title":{"rendered":"\u90fd\u662f\u540c\u6a23\u689d\u4ef6\u7684 MySQL Select \u8a9e\u53e5\uff0c\u70ba\u4f55\u8b80\u5230\u7684\u5167\u5bb9\u537b\u4e0d\u4e00\u6a23\uff1f"},"content":{"rendered":"<h1 id=\"%e9%83%bd%e6%98%af%e5%90%8c%e6%a8%a3%e6%a2%9d%e4%bb%b6%e7%9a%84-mysql-select-%e8%aa%9e%e5%8f%a5%ef%bc%8c%e7%82%ba%e4%bd%95%e8%ae%80%e5%88%b0%e7%9a%84%e5%85%a7%e5%ae%b9%e5%8d%bb%e4%b8%8d%e4%b8%80-NhpOOnIfOk\">\u90fd\u662f\u540c\u6a23\u689d\u4ef6\u7684 MySQL Select \u8a9e\u53e5\uff0c\u70ba\u4f55\u8b80\u5230\u7684\u5167\u5bb9\u537b\u4e0d\u4e00\u6a23\uff1f<\/h1>\n<p>\u5728\u4f7f\u7528 MySQL \u6578\u64da\u5eab\u6642\uff0c\u958b\u767c\u8005\u7d93\u5e38\u6703\u9047\u5230\u540c\u6a23\u7684 <code>SELECT<\/code> \u8a9e\u53e5\u537b\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u9019\u7a2e\u60c5\u6cc1\u53ef\u80fd\u6703\u8b93\u4eba\u611f\u5230\u56f0\u60d1\uff0c\u5c24\u5176\u662f\u5728\u6578\u64da\u5eab\u7684\u8a2d\u8a08\u548c\u67e5\u8a62\u908f\u8f2f\u4e0a\u90fd\u6c92\u6709\u660e\u986f\u554f\u984c\u7684\u60c5\u6cc1\u4e0b\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u9020\u6210\u9019\u7a2e\u73fe\u8c61\u7684\u5e7e\u500b\u4e3b\u8981\u539f\u56e0\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3 MySQL \u7684\u884c\u70ba\u3002<\/p>\n<h2 id=\"1-%e6%95%b8%e6%93%9a%e5%ba%ab%e7%9a%84%e9%9a%94%e9%9b%a2%e7%b4%9a%e5%88%a5-NhpOOnIfOk\">1. \u6578\u64da\u5eab\u7684\u9694\u96e2\u7d1a\u5225<\/h2>\n<p>MySQL \u652f\u6301\u591a\u7a2e\u4e8b\u52d9\u9694\u96e2\u7d1a\u5225\uff0c\u5305\u62ec <code>READ UNCOMMITTED<\/code>\u3001<code>READ COMMITTED<\/code>\u3001<code>REPEATABLE READ<\/code> \u548c <code>SERIALIZABLE<\/code>\u3002\u9019\u4e9b\u9694\u96e2\u7d1a\u5225\u6703\u5f71\u97ff\u5230\u67e5\u8a62\u6642\u80fd\u5920\u8b80\u53d6\u5230\u7684\u6578\u64da\u3002<\/p>\n<ul>\n<li><strong>READ UNCOMMITTED<\/strong>: \u5141\u8a31\u8b80\u53d6\u672a\u63d0\u4ea4\u7684\u6578\u64da\uff0c\u53ef\u80fd\u6703\u5c0e\u81f4\u8b80\u53d6\u5230\u81e8\u6642\u6578\u64da\u3002<\/li>\n<li><strong>READ COMMITTED<\/strong>: \u53ea\u5141\u8a31\u8b80\u53d6\u5df2\u63d0\u4ea4\u7684\u6578\u64da\uff0c\u907f\u514d\u4e86\u81e8\u6642\u6578\u64da\u7684\u5f71\u97ff\u3002<\/li>\n<li><strong>REPEATABLE READ<\/strong>: \u5728\u540c\u4e00\u4e8b\u52d9\u4e2d\u591a\u6b21\u57f7\u884c\u76f8\u540c\u7684\u67e5\u8a62\u6703\u8fd4\u56de\u76f8\u540c\u7684\u7d50\u679c\uff0c\u5373\u4f7f\u5176\u4ed6\u4e8b\u52d9\u5df2\u7d93\u63d0\u4ea4\u4e86\u8b8a\u66f4\u3002<\/li>\n<li><strong>SERIALIZABLE<\/strong>: \u6700\u56b4\u683c\u7684\u9694\u96e2\u7d1a\u5225\uff0c\u78ba\u4fdd\u4e8b\u52d9\u4e4b\u9593\u5b8c\u5168\u9694\u96e2\u3002<\/li>\n<\/ul>\n<p>\u56e0\u6b64\uff0c\u5982\u679c\u5728\u4e0d\u540c\u7684\u4e8b\u52d9\u4e2d\u57f7\u884c\u76f8\u540c\u7684 <code>SELECT<\/code> \u8a9e\u53e5\uff0c\u53ef\u80fd\u6703\u56e0\u70ba\u9694\u96e2\u7d1a\u5225\u7684\u4e0d\u540c\u800c\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002<\/p>\n<h2 id=\"2-%e6%95%b8%e6%93%9a%e7%9a%84%e8%ae%8a%e6%9b%b4-NhpOOnIfOk\">2. \u6578\u64da\u7684\u8b8a\u66f4<\/h2>\n<p>\u5728\u591a\u7528\u6236\u74b0\u5883\u4e2d\uff0c\u6578\u64da\u5eab\u4e2d\u7684\u6578\u64da\u53ef\u80fd\u6703\u88ab\u5176\u4ed6\u7528\u6236\u6216\u61c9\u7528\u7a0b\u5e8f\u4fee\u6539\u3002\u5373\u4f7f\u5728\u76f8\u540c\u7684\u67e5\u8a62\u689d\u4ef6\u4e0b\uff0c\u5982\u679c\u5728\u67e5\u8a62\u57f7\u884c\u4e4b\u524d\u6216\u4e4b\u5f8c\u6709\u5176\u4ed6\u4e8b\u52d9\u5c0d\u6578\u64da\u9032\u884c\u4e86\u63d2\u5165\u3001\u66f4\u65b0\u6216\u522a\u9664\u64cd\u4f5c\uff0c\u5247\u67e5\u8a62\u7d50\u679c\u4e5f\u6703\u6709\u6240\u4e0d\u540c\u3002<\/p>\n<pre><code>-- \u5047\u8a2d\u6709\u4e00\u500b\u540d\u70ba users \u7684\u8868\nSELECT * FROM users WHERE age &gt; 30;\n<\/code><\/pre>\n<p>\u5982\u679c\u5728\u57f7\u884c\u4e0a\u8ff0\u67e5\u8a62\u4e4b\u524d\uff0c\u6709\u5176\u4ed6\u7528\u6236\u63d2\u5165\u4e86\u4e00\u689d\u5e74\u9f61\u70ba 35 \u7684\u8a18\u9304\uff0c\u90a3\u9ebc\u67e5\u8a62\u7d50\u679c\u5c07\u6703\u5305\u542b\u9019\u689d\u65b0\u8a18\u9304\u3002<\/p>\n<h2 id=\"3-%e6%9f%a5%e8%a9%a2%e7%b7%a9%e5%ad%98-NhpOOnIfOk\">3. \u67e5\u8a62\u7de9\u5b58<\/h2>\n<p>MySQL \u6709\u4e00\u500b\u67e5\u8a62\u7de9\u5b58\u6a5f\u5236\uff0c\u7576\u76f8\u540c\u7684\u67e5\u8a62\u88ab\u591a\u6b21\u57f7\u884c\u6642\uff0cMySQL \u53ef\u80fd\u6703\u8fd4\u56de\u7de9\u5b58\u4e2d\u7684\u7d50\u679c\uff0c\u800c\u4e0d\u662f\u91cd\u65b0\u57f7\u884c\u67e5\u8a62\u3002\u9019\u53ef\u80fd\u5c0e\u81f4\u5728\u6578\u64da\u8b8a\u66f4\u5f8c\uff0c\u4ecd\u7136\u8fd4\u56de\u820a\u7684\u7d50\u679c\u3002<\/p>\n<p>\u8981\u7981\u7528\u67e5\u8a62\u7de9\u5b58\uff0c\u53ef\u4ee5\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528 <code>SQL_NO_CACHE<\/code> \u4f86\u5f37\u5236 MySQL \u91cd\u65b0\u57f7\u884c\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT SQL_NO_CACHE * FROM users WHERE age &gt; 30;\n<\/code><\/pre>\n<h2 id=\"4-%e6%95%b8%e6%93%9a%e5%ba%ab%e7%9a%84%e8%a4%87%e8%a3%bd%e5%bb%b6%e9%81%b2-NhpOOnIfOk\">4. \u6578\u64da\u5eab\u7684\u8907\u88fd\u5ef6\u9072<\/h2>\n<p>\u5728\u4f7f\u7528\u4e3b\u5f9e\u8907\u88fd\u7684\u6578\u64da\u5eab\u67b6\u69cb\u4e2d\uff0c\u4e3b\u6578\u64da\u5eab\u7684\u8b8a\u66f4\u53ef\u80fd\u9700\u8981\u6642\u9593\u624d\u80fd\u540c\u6b65\u5230\u5f9e\u6578\u64da\u5eab\u3002\u5982\u679c\u5728\u5f9e\u6578\u64da\u5eab\u4e0a\u57f7\u884c\u67e5\u8a62\uff0c\u53ef\u80fd\u6703\u56e0\u70ba\u8907\u88fd\u5ef6\u9072\u800c\u8b80\u53d6\u5230\u4e0d\u4e00\u81f4\u7684\u6578\u64da\u3002<\/p>\n<h2 id=\"5-%e9%9a%a8%e6%a9%9f%e6%80%a7%e5%92%8c%e6%8e%92%e5%ba%8f-NhpOOnIfOk\">5. \u96a8\u6a5f\u6027\u548c\u6392\u5e8f<\/h2>\n<p>\u5982\u679c\u67e5\u8a62\u4e2d\u4f7f\u7528\u4e86\u96a8\u6a5f\u6392\u5e8f\u6216\u9650\u5236\u689d\u4ef6\uff0c\u5247\u6bcf\u6b21\u57f7\u884c\u67e5\u8a62\u6642\u8fd4\u56de\u7684\u7d50\u679c\u96c6\u53ef\u80fd\u6703\u6709\u6240\u4e0d\u540c\u3002\u4f8b\u5982\uff0c\u4f7f\u7528 <code>ORDER BY RAND()<\/code> \u7684\u67e5\u8a62\u6bcf\u6b21\u57f7\u884c\u90fd\u6703\u96a8\u6a5f\u8fd4\u56de\u4e0d\u540c\u7684\u884c\u3002<\/p>\n<pre><code>SELECT * FROM users ORDER BY RAND() LIMIT 5;\n<\/code><\/pre>\n<h2 id=\"%e7%b8%bd%e7%b5%90-NhpOOnIfOk\">\u7e3d\u7d50<\/h2>\n<p>\u5728 MySQL \u4e2d\uff0c\u5373\u4f7f\u662f\u76f8\u540c\u7684 <code>SELECT<\/code> \u8a9e\u53e5\uff0c\u56e0\u70ba\u4e8b\u52d9\u9694\u96e2\u7d1a\u5225\u3001\u6578\u64da\u8b8a\u66f4\u3001\u67e5\u8a62\u7de9\u5b58\u3001\u6578\u64da\u5eab\u8907\u88fd\u5ef6\u9072\u4ee5\u53ca\u96a8\u6a5f\u6027\u7b49\u56e0\u7d20\uff0c\u53ef\u80fd\u6703\u5c0e\u81f4\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u4e86\u89e3\u9019\u4e9b\u56e0\u7d20\u6709\u52a9\u65bc\u958b\u767c\u8005\u66f4\u597d\u5730\u8a2d\u8a08\u548c\u512a\u5316\u67e5\u8a62\uff0c\u78ba\u4fdd\u6578\u64da\u7684\u4e00\u81f4\u6027\u548c\u6e96\u78ba\u6027\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u7a69\u5b9a\u4e14\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u60a8\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f\u6578\u64da\u5eab\u7ba1\u7406\u9084\u662f\u61c9\u7528\u90e8\u7f72\uff0c\u6211\u5011\u7684 <a href=\"https:\/\/server.hk\">\u4f3a\u670d\u5668<\/a> \u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u8a0e\u5728\u76f8\u540c\u689d\u4ef6\u4e0b\uff0cMySQL Select \u8a9e\u53e5\u70ba\u4f55\u8b80\u53d6\u7684\u5167\u5bb9\u6703\u6709\u6240\u4e0d\u540c\uff0c\u63ed\u793a\u6f5b\u5728\u7684\u6578\u64da\u4e00\u81f4\u6027\u554f\u984c\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-154411","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/154411","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=154411"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/154411\/revisions"}],"predecessor-version":[{"id":154412,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/154411\/revisions\/154412"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=154411"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=154411"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=154411"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}