{"id":74363,"date":"2024-10-15T22:22:15","date_gmt":"2024-10-15T14:22:15","guid":{"rendered":"https:\/\/server.hk\/cnblog\/74363\/"},"modified":"2024-10-15T22:22:15","modified_gmt":"2024-10-15T14:22:15","slug":"mysql-explain%e5%af%a6%e9%9a%9b%e6%93%8d%e4%bd%9c%e6%b5%81%e7%a8%8b%e8%aa%aa%e6%98%8e","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/74363\/","title":{"rendered":"MySQL explain\u5be6\u969b\u64cd\u4f5c\u6d41\u7a0b\u8aaa\u660e"},"content":{"rendered":"<h1 id=\"mysql-explain%e5%af%a6%e9%9a%9b%e6%93%8d%e4%bd%9c%e6%b5%81%e7%a8%8b%e8%aa%aa%e6%98%8e-nSFpRLgZhl\">MySQL Explain\u5be6\u969b\u64cd\u4f5c\u6d41\u7a0b\u8aaa\u660e<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u806f\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u7576\u6211\u5011\u9032\u884c\u67e5\u8a62\u6642\uff0c\u4e86\u89e3\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\u662f\u975e\u5e38\u91cd\u8981\u7684\uff0c\u9019\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u512a\u5316\u6027\u80fd\u3002MySQL\u63d0\u4f9b\u4e86\u4e00\u500b\u540d\u70baEXPLAIN\u7684\u547d\u4ee4\uff0c\u80fd\u5920\u986f\u793a\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\u3002\u672c\u6587\u5c07\u8a73\u7d30\u4ecb\u7d39MySQL\u7684EXPLAIN\u547d\u4ee4\u7684\u5be6\u969b\u64cd\u4f5c\u6d41\u7a0b\u53ca\u5176\u61c9\u7528\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afexplain%e5%91%bd%e4%bb%a4%ef%bc%9f-nSFpRLgZhl\">\u4ec0\u9ebc\u662fEXPLAIN\u547d\u4ee4\uff1f<\/h2>\n<p>EXPLAIN\u547d\u4ee4\u7528\u65bc\u5206\u6790SQL\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\u3002\u5b83\u80fd\u5920\u544a\u8a34\u6211\u5011MySQL\u5c07\u5982\u4f55\u57f7\u884c\u67e5\u8a62\uff0c\u5305\u62ec\u4f7f\u7528\u7684\u7d22\u5f15\u3001\u8868\u7684\u806f\u63a5\u9806\u5e8f\u3001\u9810\u671f\u7684\u884c\u6578\u7b49\u3002\u9019\u4e9b\u4fe1\u606f\u5c0d\u65bc\u512a\u5316\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-nSFpRLgZhl\">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\uff0ctable_name\u662f\u4f60\u8981\u67e5\u8a62\u7684\u8868\u540d\uff0ccondition\u662f\u67e5\u8a62\u7684\u689d\u4ef6\u3002\u57f7\u884c\u9019\u500b\u547d\u4ee4\u5f8c\uff0cMySQL\u5c07\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%e8%ae%80-nSFpRLgZhl\">EXPLAIN\u547d\u4ee4\u7684\u8f38\u51fa\u89e3\u8b80<\/h2>\n<p>EXPLAIN\u547d\u4ee4\u7684\u8f38\u51fa\u901a\u5e38\u5305\u542b\u4ee5\u4e0b\u5e7e\u500b\u91cd\u8981\u5b57\u6bb5\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\u6211\u5011\u7406\u89e3\u67e5\u8a62\u7684\u57f7\u884c\u9806\u5e8f\u3002<\/li>\n<li><strong>select_type<\/strong>\uff1a\u67e5\u8a62\u7684\u985e\u578b\uff0c\u4f8b\u5982\u7c21\u55ae\u67e5\u8a62\u3001\u806f\u63a5\u67e5\u8a62\u7b49\u3002<\/li>\n<li><strong>table<\/strong>\uff1a\u6b63\u5728\u67e5\u8a62\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\u6700\u512a\u5230\u6700\u52a3\u4f9d\u6b21\u70ba\uff1asystem\u3001const\u3001eq_ref\u3001ref\u3001range\u3001index\u3001ALL\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\u671f\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%af%a6%e9%9a%9b%e6%93%8d%e4%bd%9c%e7%a4%ba%e4%be%8b-nSFpRLgZhl\">\u5be6\u969b\u64cd\u4f5c\u793a\u4f8b<\/h2>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba<code>employees<\/code>\u7684\u8868\uff0c\u4e26\u4e14\u6211\u5011\u60f3\u8981\u67e5\u8a62\u6240\u6709\u5e74\u9f61\u5927\u65bc30\u7684\u54e1\u5de5\u3002\u9996\u5148\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528EXPLAIN\u547d\u4ee4\u4f86\u5206\u6790\u9019\u500b\u67e5\u8a62\uff1a<\/p>\n<pre><code>EXPLAIN SELECT * FROM employees WHERE age &gt; 30;<\/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 | Extra       |\n+----+-------------+----------+-------+---------------+---------+---------+-------+------+-------------+\n|  1 | SIMPLE      | employees | range | age_index     | age_index| 4       | NULL  |  100 | Using where |\n+----+-------------+----------+-------+---------------+---------+---------+-------+------+-------------+\n<\/code><\/pre>\n<p>\u5f9e\u9019\u500b\u7d50\u679c\u4e2d\uff0c\u6211\u5011\u53ef\u4ee5\u770b\u5230\uff1a<\/p>\n<ul>\n<li>\u67e5\u8a62\u985e\u578b\u70baSIMPLE\uff0c\u8868\u793a\u9019\u662f\u4e00\u500b\u7c21\u55ae\u67e5\u8a62\u3002<\/li>\n<li>\u4f7f\u7528\u4e86<code>age_index<\/code>\u7d22\u5f15\uff0c\u9019\u610f\u5473\u8457\u67e5\u8a62\u6548\u7387\u8f03\u9ad8\u3002<\/li>\n<li>\u9810\u671f\u6383\u63cf\u7684\u884c\u6578\u70ba100\uff0c\u9019\u662f\u6211\u5011\u9700\u8981\u8003\u616e\u7684\u6027\u80fd\u6307\u6a19\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%84%aa%e5%8c%96%e6%9f%a5%e8%a9%a2%e7%9a%84%e5%bb%ba%e8%ad%b0-nSFpRLgZhl\">\u512a\u5316\u67e5\u8a62\u7684\u5efa\u8b70<\/h2>\n<p>\u6839\u64daEXPLAIN\u7684\u8f38\u51fa\uff0c\u6211\u5011\u53ef\u4ee5\u9032\u884c\u4ee5\u4e0b\u512a\u5316\uff1a<\/p>\n<ul>\n<li>\u78ba\u4fdd\u9069\u7576\u7684\u7d22\u5f15\u5b58\u5728\uff0c\u7279\u5225\u662f\u5728\u67e5\u8a62\u689d\u4ef6\u4e2d\u4f7f\u7528\u7684\u5217\u4e0a\u3002<\/li>\n<li>\u907f\u514d\u4f7f\u7528SELECT *\uff0c\u53ea\u9078\u64c7\u9700\u8981\u7684\u5217\uff0c\u4ee5\u6e1b\u5c11\u6578\u64da\u50b3\u8f38\u91cf\u3002<\/li>\n<li>\u8003\u616e\u91cd\u5beb\u67e5\u8a62\u4ee5\u63d0\u9ad8\u6548\u7387\uff0c\u4f8b\u5982\u4f7f\u7528JOIN\u800c\u4e0d\u662f\u5b50\u67e5\u8a62\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-nSFpRLgZhl\">\u7e3d\u7d50<\/h2>\n<p>MySQL\u7684EXPLAIN\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\u7406\u89e3\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\uff0c\u5f9e\u800c\u9032\u884c\u6709\u6548\u7684\u6027\u80fd\u512a\u5316\u3002\u901a\u904e\u5206\u6790EXPLAIN\u7684\u8f38\u51fa\uff0c\u6211\u5011\u53ef\u4ee5\u8b58\u5225\u6f5b\u5728\u7684\u6027\u80fd\u74f6\u9838\u4e26\u9032\u884c\u76f8\u61c9\u7684\u8abf\u6574\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u61c9\u7528\uff0c\u9078\u64c7\u5408\u9069\u7684<code><a href=\"https:\/\/server.hk\">VPS<\/a><\/code>\u6216<code><a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a><\/code>\u89e3\u6c7a\u65b9\u6848\u4e5f\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u7684EXPLAIN\u6307\u4ee4\uff0c\u638c\u63e1\u67e5\u8a62\u512a\u5316\u7684\u5be6\u969b\u64cd\u4f5c\u6d41\u7a0b\uff0c\u63d0\u5347\u6578\u64da\u5eab\u6027\u80fd\u8207\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-74363","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/74363","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=74363"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/74363\/revisions"}],"predecessor-version":[{"id":74364,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/74363\/revisions\/74364"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=74363"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=74363"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=74363"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}