{"id":194147,"date":"2024-11-13T04:10:25","date_gmt":"2024-11-12T20:10:25","guid":{"rendered":"https:\/\/server.hk\/cnblog\/194147\/"},"modified":"2024-11-13T04:10:27","modified_gmt":"2024-11-12T20:10:27","slug":"%e4%b8%80%e6%a2%9dsql%e6%9f%a5%e8%a9%a2%e8%aa%9e%e5%8f%a5%e6%98%af%e5%a6%82%e4%bd%95%e5%9f%b7%e8%a1%8c%e7%9a%84%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/194147\/","title":{"rendered":"\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u662f\u5982\u4f55\u57f7\u884c\u7684\uff1f"},"content":{"rendered":"<h1 id=\"%e4%b8%80%e6%a2%9dsql%e6%9f%a5%e8%a9%a2%e8%aa%9e%e5%8f%a5%e6%98%af%e5%a6%82%e4%bd%95%e5%9f%b7%e8%a1%8c%e7%9a%84%ef%bc%9f-zUhhtaKViF\">\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u662f\u5982\u4f55\u57f7\u884c\u7684\uff1f<\/h1>\n<p>SQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u7528\u65bc\u7ba1\u7406\u548c\u64cd\u4f5c\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u7684\u6a19\u6e96\u8a9e\u8a00\u3002\u7576\u6211\u5011\u57f7\u884c\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u6642\uff0c\u80cc\u5f8c\u6d89\u53ca\u591a\u500b\u6b65\u9a5f\u548c\u904e\u7a0b\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u7684\u57f7\u884c\u904e\u7a0b\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u6578\u64da\u5eab\u7684\u904b\u4f5c\u539f\u7406\u3002<\/p>\n<h2 id=\"1-sql%e6%9f%a5%e8%a9%a2%e7%9a%84%e8%a7%a3%e6%9e%90-zUhhtaKViF\">1. SQL\u67e5\u8a62\u7684\u89e3\u6790<\/h2>\n<p>\u7576\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u88ab\u63d0\u4ea4\u5230\u6578\u64da\u5eab\u6642\uff0c\u7b2c\u4e00\u6b65\u662f\u89e3\u6790\uff08Parsing\uff09\u3002\u5728\u9019\u500b\u968e\u6bb5\uff0c\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\uff08DBMS\uff09\u6703\u6aa2\u67e5\u8a9e\u6cd5\u7684\u6b63\u78ba\u6027\uff0c\u78ba\u4fdd\u67e5\u8a62\u7b26\u5408SQL\u8a9e\u8a00\u7684\u898f\u7bc4\u3002\u5982\u679c\u8a9e\u6cd5\u6b63\u78ba\uff0c\u7cfb\u7d71\u6703\u5c07\u67e5\u8a62\u8f49\u63db\u70ba\u4e00\u500b\u5167\u90e8\u8868\u793a\u5f62\u5f0f\uff0c\u901a\u5e38\u662f\u6a39\u72c0\u7d50\u69cb\u3002<\/p>\n<pre><code>SELECT * FROM users WHERE age &gt; 18;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u67e5\u8a62\u6703\u88ab\u89e3\u6790\u70ba\u4e00\u500b\u6a39\u72c0\u7d50\u69cb\uff0c\u8868\u793a\u5f9e\u201cusers\u201d\u8868\u4e2d\u9078\u64c7\u6240\u6709\u5e74\u9f61\u5927\u65bc18\u7684\u7528\u6236\u3002<\/p>\n<h2 id=\"2-%e6%9f%a5%e8%a9%a2%e5%84%aa%e5%8c%96-zUhhtaKViF\">2. \u67e5\u8a62\u512a\u5316<\/h2>\n<p>\u89e3\u6790\u5f8c\uff0c\u6578\u64da\u5eab\u6703\u9032\u5165\u67e5\u8a62\u512a\u5316\uff08Optimization\uff09\u968e\u6bb5\u3002\u9019\u500b\u904e\u7a0b\u7684\u76ee\u7684\u662f\u751f\u6210\u4e00\u500b\u57f7\u884c\u8a08\u5283\uff0c\u4ee5\u6700\u6709\u6548\u7684\u65b9\u5f0f\u57f7\u884c\u67e5\u8a62\u3002\u512a\u5316\u5668\u6703\u8003\u616e\u591a\u7a2e\u56e0\u7d20\uff0c\u5305\u62ec\u6578\u64da\u8868\u7684\u5927\u5c0f\u3001\u7d22\u5f15\u7684\u5b58\u5728\u8207\u5426\u3001\u4ee5\u53ca\u5176\u4ed6\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u5982\u679c\u201cusers\u201d\u8868\u4e0a\u6709\u4e00\u500b\u91dd\u5c0d\u201cage\u201d\u5217\u7684\u7d22\u5f15\uff0c\u512a\u5316\u5668\u53ef\u80fd\u6703\u9078\u64c7\u4f7f\u7528\u9019\u500b\u7d22\u5f15\u4f86\u52a0\u901f\u67e5\u8a62\u7684\u57f7\u884c\u3002<\/p>\n<h2 id=\"3-%e5%9f%b7%e8%a1%8c%e8%a8%88%e5%8a%83%e7%9a%84%e7%94%9f%e6%88%90-zUhhtaKViF\">3. \u57f7\u884c\u8a08\u5283\u7684\u751f\u6210<\/h2>\n<p>\u5728\u512a\u5316\u904e\u7a0b\u7d50\u675f\u5f8c\uff0c\u6578\u64da\u5eab\u6703\u751f\u6210\u4e00\u500b\u5177\u9ad4\u7684\u57f7\u884c\u8a08\u5283\uff08Execution Plan\uff09\u3002\u9019\u500b\u8a08\u5283\u8a73\u7d30\u63cf\u8ff0\u4e86\u5982\u4f55\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u6240\u9700\u7684\u6578\u64da\uff0c\u5305\u62ec\u4f7f\u7528\u54ea\u4e9b\u7d22\u5f15\u3001\u5982\u4f55\u9023\u63a5\u8868\u3001\u4ee5\u53ca\u5982\u4f55\u904e\u6ffe\u6578\u64da\u7b49\u3002<\/p>\n<pre><code>EXPLAIN SELECT * FROM users WHERE age &gt; 18;<\/code><\/pre>\n<p>\u4f7f\u7528\u201cEXPLAIN\u201d\u8a9e\u53e5\u53ef\u4ee5\u67e5\u770b\u57f7\u884c\u8a08\u5283\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u7406\u89e3\u67e5\u8a62\u7684\u6027\u80fd\u3002<\/p>\n<h2 id=\"4-%e6%9f%a5%e8%a9%a2%e7%9a%84%e5%9f%b7%e8%a1%8c-zUhhtaKViF\">4. \u67e5\u8a62\u7684\u57f7\u884c<\/h2>\n<p>\u4e00\u65e6\u57f7\u884c\u8a08\u5283\u751f\u6210\uff0c\u6578\u64da\u5eab\u5c07\u958b\u59cb\u57f7\u884c\u67e5\u8a62\u3002\u9019\u500b\u904e\u7a0b\u5305\u62ec\u4ee5\u4e0b\u5e7e\u500b\u6b65\u9a5f\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u6aa2\u7d22\uff1a<\/strong>\u6839\u64da\u57f7\u884c\u8a08\u5283\uff0c\u6578\u64da\u5eab\u6703\u5f9e\u78c1\u789f\u4e2d\u6aa2\u7d22\u6240\u9700\u7684\u6578\u64da\u3002<\/li>\n<li><strong>\u6578\u64da\u904e\u6ffe\uff1a<\/strong>\u6839\u64daWHERE\u5b50\u53e5\u7684\u689d\u4ef6\u904e\u6ffe\u6578\u64da\uff0c\u53ea\u4fdd\u7559\u7b26\u5408\u689d\u4ef6\u7684\u8a18\u9304\u3002<\/li>\n<li><strong>\u6578\u64da\u8fd4\u56de\uff1a<\/strong>\u5c07\u6700\u7d42\u7d50\u679c\u96c6\u8fd4\u56de\u7d66\u7528\u6236\u6216\u61c9\u7528\u7a0b\u5e8f\u3002<\/li>\n<\/ul>\n<h2 id=\"5-%e7%b5%90%e6%9e%9c%e7%9a%84%e8%bf%94%e5%9b%9e-zUhhtaKViF\">5. \u7d50\u679c\u7684\u8fd4\u56de<\/h2>\n<p>\u67e5\u8a62\u57f7\u884c\u5b8c\u7562\u5f8c\uff0c\u6578\u64da\u5eab\u6703\u5c07\u7d50\u679c\u96c6\u8fd4\u56de\u7d66\u7528\u6236\u3002\u9019\u4e9b\u7d50\u679c\u53ef\u4ee5\u662f\u55ae\u884c\u3001\u591a\u884c\u6216\u7a7a\u96c6\uff0c\u5177\u9ad4\u53d6\u6c7a\u65bc\u67e5\u8a62\u7684\u689d\u4ef6\u548c\u6578\u64da\u5eab\u4e2d\u7684\u6578\u64da\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-zUhhtaKViF\">\u7e3d\u7d50<\/h2>\n<p>\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u7684\u57f7\u884c\u904e\u7a0b\u6d89\u53ca\u89e3\u6790\u3001\u512a\u5316\u3001\u57f7\u884c\u8a08\u5283\u751f\u6210\u3001\u67e5\u8a62\u57f7\u884c\u548c\u7d50\u679c\u8fd4\u56de\u7b49\u591a\u500b\u6b65\u9a5f\u3002\u4e86\u89e3\u9019\u4e9b\u904e\u7a0b\u4e0d\u50c5\u6709\u52a9\u65bc\u958b\u767c\u8005\u64b0\u5beb\u66f4\u9ad8\u6548\u7684\u67e5\u8a62\uff0c\u9084\u80fd\u5e6b\u52a9\u4ed6\u5011\u5728\u9762\u5c0d\u6027\u80fd\u554f\u984c\u6642\u9032\u884c\u8abf\u8a66\u548c\u512a\u5316\u3002\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u548c\u6027\u80fd\u512a\u5316\u6709\u9032\u4e00\u6b65\u7684\u9700\u6c42\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u6216<a href=\"https:\/\/server.hk\">\u96f2\u4f3a\u670d\u5668<\/a>\u4f86\u63d0\u5347\u60a8\u7684\u61c9\u7528\u6027\u80fd\u548c\u7a69\u5b9a\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3\u4e00\u689dSQL\u67e5\u8a62\u8a9e\u53e5\u7684\u57f7\u884c\u904e\u7a0b\uff0c\u5305\u62ec\u89e3\u6790\u3001\u512a\u5316\u548c\u57f7\u884c\u968e\u6bb5\uff0c\u63ed\u793a\u6578\u64da\u5eab\u5982\u4f55\u8655\u7406\u8acb\u6c42\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-194147","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/194147","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=194147"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/194147\/revisions"}],"predecessor-version":[{"id":194148,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/194147\/revisions\/194148"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=194147"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=194147"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=194147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}