{"id":191402,"date":"2024-11-12T16:37:23","date_gmt":"2024-11-12T08:37:23","guid":{"rendered":"https:\/\/server.hk\/cnblog\/191402\/"},"modified":"2024-11-12T16:37:24","modified_gmt":"2024-11-12T08:37:24","slug":"%e8%a9%b3%e8%a7%a3mysql%e4%b8%adexplain%e8%a7%a3%e9%87%8b%e5%91%bd%e4%bb%a4","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/191402\/","title":{"rendered":"\u8a73\u89e3MySQL\u4e2dEXPLAIN\u89e3\u91cb\u547d\u4ee4"},"content":{"rendered":"<h1 id=\"%e8%a9%b3%e8%a7%a3mysql%e4%b8%adexplain%e8%a7%a3%e9%87%8b%e5%91%bd%e4%bb%a4-MbEuBUciGT\">\u8a73\u89e3MySQL\u4e2dEXPLAIN\u89e3\u91cb\u547d\u4ee4<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u6027\u80fd\u512a\u5316\u662f\u78ba\u4fdd\u61c9\u7528\u7a0b\u5e8f\u9ad8\u6548\u904b\u884c\u7684\u95dc\u9375\u56e0\u7d20\u4e4b\u4e00\u3002MySQL\u4f5c\u70ba\u4e00\u500b\u6d41\u884c\u7684\u958b\u6e90\u6578\u64da\u5eab\u7cfb\u7d71\uff0c\u63d0\u4f9b\u4e86\u591a\u7a2e\u5de5\u5177\u4f86\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5eab\u7ba1\u7406\u54e1\u5206\u6790\u67e5\u8a62\u6027\u80fd\u3002\u5176\u4e2d\uff0c<code>EXPLAIN<\/code>\u547d\u4ee4\u662f\u4e00\u500b\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5e6b\u52a9\u7528\u6236\u7406\u89e3\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\uff0c\u5f9e\u800c\u9032\u884c\u76f8\u61c9\u7684\u512a\u5316\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afexplain%e5%91%bd%e4%bb%a4%ef%bc%9f-MbEuBUciGT\">\u4ec0\u9ebc\u662fEXPLAIN\u547d\u4ee4\uff1f<\/h2>\n<p><code>EXPLAIN<\/code>\u547d\u4ee4\u7528\u65bc\u986f\u793aMySQL\u57f7\u884c\u67e5\u8a62\u7684\u8a08\u5283\u3002\u7576\u4f60\u5728\u67e5\u8a62\u524d\u52a0\u4e0a<code>EXPLAIN<\/code>\uff0cMySQL\u6703\u8fd4\u56de\u4e00\u500b\u8868\u683c\uff0c\u986f\u793a\u67e5\u8a62\u7684\u57f7\u884c\u6b65\u9a5f\uff0c\u5305\u62ec\u4f7f\u7528\u7684\u7d22\u5f15\u3001\u8868\u7684\u806f\u63a5\u9806\u5e8f\u3001\u9810\u4f30\u7684\u884c\u6578\u7b49\u4fe1\u606f\u3002\u9019\u4e9b\u4fe1\u606f\u5c0d\u65bc\u5206\u6790\u67e5\u8a62\u6027\u80fd\u81f3\u95dc\u91cd\u8981\u3002<\/p>\n<h2 id=\"explain%e5%91%bd%e4%bb%a4%e7%9a%84%e5%9f%ba%e6%9c%ac%e8%aa%9e%e6%b3%95-MbEuBUciGT\">EXPLAIN\u547d\u4ee4\u7684\u57fa\u672c\u8a9e\u6cd5<\/h2>\n<pre><code>EXPLAIN SELECT * FROM table_name WHERE condition;<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>table_name<\/code>\u662f\u4f60\u8981\u67e5\u8a62\u7684\u8868\u540d\uff0c<code>condition<\/code>\u662f\u67e5\u8a62\u7684\u689d\u4ef6\u3002\u57f7\u884c\u9019\u500b\u547d\u4ee4\u5f8c\uff0cMySQL\u6703\u8fd4\u56de\u4e00\u500b\u7d50\u679c\u96c6\uff0c\u986f\u793a\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\u3002<\/p>\n<h2 id=\"explain%e5%91%bd%e4%bb%a4%e7%9a%84%e8%bc%b8%e5%87%ba%e8%a7%a3%e9%87%8b-MbEuBUciGT\">EXPLAIN\u547d\u4ee4\u7684\u8f38\u51fa\u89e3\u91cb<\/h2>\n<p>\u57f7\u884c<code>EXPLAIN<\/code>\u547d\u4ee4\u5f8c\uff0c\u8fd4\u56de\u7684\u7d50\u679c\u96c6\u901a\u5e38\u5305\u542b\u4ee5\u4e0b\u5e7e\u500b\u91cd\u8981\u7684\u5217\uff1a<\/p>\n<ul>\n<li><strong>id<\/strong>\uff1a\u67e5\u8a62\u7684\u8b58\u5225\u78bc\uff0c\u5c0d\u65bc\u8907\u96dc\u67e5\u8a62\uff0c\u9019\u500b\u503c\u53ef\u4ee5\u5e6b\u52a9\u8b58\u5225\u4e0d\u540c\u7684\u67e5\u8a62\u90e8\u5206\u3002<\/li>\n<li><strong>select_type<\/strong>\uff1a\u67e5\u8a62\u7684\u985e\u578b\uff0c\u4f8b\u5982<code>SIMPLE<\/code>\uff08\u7c21\u55ae\u67e5\u8a62\uff09\u3001<code>PRIMARY<\/code>\uff08\u4e3b\u67e5\u8a62\uff09\u7b49\u3002<\/li>\n<li><strong>table<\/strong>\uff1a\u6b63\u5728\u8a2a\u554f\u7684\u8868\u540d\u3002<\/li>\n<li><strong>type<\/strong>\uff1a\u806f\u63a5\u985e\u578b\uff0c\u986f\u793a\u67e5\u8a62\u7684\u6548\u7387\uff0c\u5f9e<code>ALL<\/code>\uff08\u5168\u8868\u6383\u63cf\uff09\u5230<code>const<\/code>\uff08\u5e38\u6578\u67e5\u8a62\uff09\u7b49\u7d1a\u5225\u3002<\/li>\n<li><strong>possible_keys<\/strong>\uff1a\u53ef\u80fd\u4f7f\u7528\u7684\u7d22\u5f15\u3002<\/li>\n<li><strong>key<\/strong>\uff1a\u5be6\u969b\u4f7f\u7528\u7684\u7d22\u5f15\u3002<\/li>\n<li><strong>rows<\/strong>\uff1a\u9810\u4f30\u9700\u8981\u6383\u63cf\u7684\u884c\u6578\u3002<\/li>\n<li><strong>Extra<\/strong>\uff1a\u984d\u5916\u7684\u4fe1\u606f\uff0c\u4f8b\u5982\u662f\u5426\u4f7f\u7528\u4e86\u81e8\u6642\u8868\u6216\u6587\u4ef6\u6392\u5e8f\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8explain%e9%80%b2%e8%a1%8c%e6%9f%a5%e8%a9%a2%e5%84%aa%e5%8c%96-MbEuBUciGT\">\u5982\u4f55\u4f7f\u7528EXPLAIN\u9032\u884c\u67e5\u8a62\u512a\u5316<\/h2>\n<p>\u4f7f\u7528<code>EXPLAIN<\/code>\u547d\u4ee4\u53ef\u4ee5\u5e6b\u52a9\u4f60\u8b58\u5225\u67e5\u8a62\u4e2d\u7684\u6027\u80fd\u74f6\u9838\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u512a\u5316\u5efa\u8b70\uff1a<\/p>\n<ul>\n<li><strong>\u6aa2\u67e5\u7d22\u5f15\u4f7f\u7528\u60c5\u6cc1<\/strong>\uff1a\u5982\u679c<code>possible_keys<\/code>\u5217\u4e2d\u6709\u7d22\u5f15\u4f46<code>key<\/code>\u5217\u70ba\u7a7a\uff0c\u5247\u53ef\u80fd\u9700\u8981\u70ba\u67e5\u8a62\u6dfb\u52a0\u7d22\u5f15\u3002<\/li>\n<li><strong>\u907f\u514d\u5168\u8868\u6383\u63cf<\/strong>\uff1a\u5982\u679c<code>type<\/code>\u986f\u793a\u70ba<code>ALL<\/code>\uff0c\u5247\u8868\u793aMySQL\u9700\u8981\u6383\u63cf\u6574\u500b\u8868\uff0c\u9019\u901a\u5e38\u6703\u5c0e\u81f4\u6027\u80fd\u4e0b\u964d\u3002\u8003\u616e\u6dfb\u52a0\u5408\u9069\u7684\u7d22\u5f15\u6216\u91cd\u69cb\u67e5\u8a62\u3002<\/li>\n<li><strong>\u5206\u6790\u806f\u63a5\u9806\u5e8f<\/strong>\uff1a<code>EXPLAIN<\/code>\u53ef\u4ee5\u986f\u793a\u8868\u7684\u806f\u63a5\u9806\u5e8f\uff0c\u78ba\u4fdd\u6700\u5c0f\u7684\u8868\u5728\u6700\u524d\u9762\uff0c\u4ee5\u6e1b\u5c11\u4e2d\u9593\u7d50\u679c\u96c6\u7684\u5927\u5c0f\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%af%a6%e9%9a%9b%e7%af%84%e4%be%8b-MbEuBUciGT\">\u5be6\u969b\u7bc4\u4f8b<\/h2>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba<code>employees<\/code>\u7684\u8868\uff0c\u4e26\u5e0c\u671b\u67e5\u8a62\u6240\u6709\u5728\u67d0\u500b\u90e8\u9580\u5de5\u4f5c\u7684\u54e1\u5de5\uff1a<\/p>\n<pre><code>EXPLAIN SELECT * FROM employees WHERE department_id = 5;<\/code><\/pre>\n<p>\u57f7\u884c\u5f8c\uff0c\u53ef\u80fd\u6703\u5f97\u5230\u5982\u4e0b\u7d50\u679c\uff1a<\/p>\n<pre><code>\n+----+-------------+-----------------+-------+---------------+---------+---------+----------------+-------+\n| id | select_type | table           | type  | possible_keys | key     | key_len | ref            | rows  |\n+----+-------------+-----------------+-------+---------------+---------+---------+----------------+-------+\n|  1 | SIMPLE      | employees       | ref   | department_id | department_id | 4       | const          |  100  |\n+----+-------------+-----------------+-------+---------------+---------+---------+----------------+-------+\n<\/code><\/pre>\n<p>\u5f9e\u9019\u500b\u7d50\u679c\u4e2d\uff0c\u6211\u5011\u53ef\u4ee5\u770b\u5230\u67e5\u8a62\u4f7f\u7528\u4e86<code>department_id<\/code>\u7d22\u5f15\uff0c\u4e26\u4e14\u9810\u4f30\u53ea\u9700\u6383\u63cf100\u884c\uff0c\u9019\u662f\u4e00\u500b\u76f8\u5c0d\u9ad8\u6548\u7684\u67e5\u8a62\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-MbEuBUciGT\">\u7e3d\u7d50<\/h2>\n<p>MySQL\u4e2d\u7684<code>EXPLAIN<\/code>\u547d\u4ee4\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5eab\u7ba1\u7406\u54e1\u5206\u6790\u548c\u512a\u5316\u67e5\u8a62\u6027\u80fd\u3002\u901a\u904e\u7406\u89e3<code>EXPLAIN<\/code>\u7684\u8f38\u51fa\uff0c\u4f7f\u7528\u8005\u53ef\u4ee5\u8b58\u5225\u6f5b\u5728\u7684\u6027\u80fd\u554f\u984c\u4e26\u9032\u884c\u76f8\u61c9\u7684\u512a\u5316\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u61c9\u7528\u7a0b\u5e8f\u4f86\u8aaa\uff0c\u638c\u63e1<code>EXPLAIN<\/code>\u7684\u4f7f\u7528\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528\u6211\u5011\u7684<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u670d\u52d9\uff0c\u63d0\u4f9b\u7a69\u5b9a\u548c\u5feb\u901f\u7684\u6578\u64da\u5eab\u652f\u6301\uff0c\u52a9\u60a8\u63d0\u5347\u696d\u52d9\u6548\u7387\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6df1\u5165\u63a2\u8a0eMySQL\u4e2d\u7684EXPLAIN\u547d\u4ee4\uff0c\u4e86\u89e3\u5176\u7528\u6cd5\u3001\u89e3\u6790\u67e5\u8a62\u8a08\u5283\uff0c\u63d0\u5347\u6578\u64da\u5eab\u6027\u80fd\u8207\u512a\u5316\u67e5\u8a62\u6548\u7387\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-191402","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/191402","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=191402"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/191402\/revisions"}],"predecessor-version":[{"id":191403,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/191402\/revisions\/191403"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=191402"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=191402"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=191402"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}