{"id":199677,"date":"2025-05-06T10:20:28","date_gmt":"2025-05-06T02:20:28","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199677\/"},"modified":"2025-05-06T10:20:28","modified_gmt":"2025-05-06T02:20:28","slug":"%e4%bd%bf%e7%94%a8mysql%e7%9a%84explain%e8%af%ad%e5%8f%a5%e8%bf%9b%e8%a1%8c%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199677\/","title":{"rendered":"\u4f7f\u7528MySQL\u7684EXPLAIN\u8bed\u53e5\u8fdb\u884c\u6027\u80fd\u4f18\u5316"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u4f7f\u7528MySQL\u7684EXPLAIN\u8bed\u53e5\u8fdb\u884c\u6027\u80fd\u4f18\u5316<\/h1>\n<p>\u7f16\u7a0b\u5e76\u4e0d\u662f\u4e00\u4e2a\u673a\u68b0\u6027\u7684\u5de5\u4f5c\uff0c\u800c\u662f\u9700\u8981\u6709\u601d\u8003\uff0c\u6709\u521b\u65b0\u7684\u5de5\u4f5c\uff0c\u8bed\u6cd5\u662f\u56fa\u5b9a\u7684\uff0c\u4f46\u89e3\u51b3\u95ee\u9898\u7684\u601d\u8def\u5219\u662f\u4f9d\u9760\u4eba\u7684\u601d\u7ef4\uff0c\u8fd9\u5c31\u9700\u8981\u6211\u4eec\u575a\u6301\u5b66\u4e60\u548c\u66f4\u65b0\u81ea\u5df1\u7684\u77e5\u8bc6\u3002\u4eca\u5929\u4e3b\u673a\u5b9d\u8d1d\u5c31\u6574\u7406\u5206\u4eab\u300a\u4f7f\u7528MySQL\u7684EXPLAIN\u8bed\u53e5\u8fdb\u884c\u6027\u80fd\u4f18\u5316\u300b\uff0c\u6587\u7ae0\u8bb2\u89e3\u7684\u77e5\u8bc6\u70b9\u4e3b\u8981\u5305\u62ec\uff0c\u5982\u679c\u4f60\u5bf9\u6570\u636e\u5e93\u65b9\u9762\u7684\u77e5\u8bc6\u70b9\u611f\u5174\u8da3\uff0c\u5c31\u4e0d\u8981\u9519\u8fc7\u4e3b\u673a\u5b9d\u8d1d\uff0c\u5728\u8fd9\u53ef\u4ee5\u5bf9\u5927\u5bb6\u7684\u77e5\u8bc6\u79ef\u7d2f\u6709\u6240\u5e2e\u52a9\uff0c\u52a9\u529b\u5f00\u53d1\u80fd\u529b\u7684\u63d0\u5347\u3002<\/p>\n<p>MySQL\u4e2d\u7684EXPLAIN\u7528\u6cd5\u8be6\u89e3\u53ca\u4ee3\u7801\u793a\u4f8b<\/p>\n<p>\u5728MySQL\u4e2d\uff0cEXPLAIN\u662f\u4e00\u4e2a\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\uff0c\u7528\u4e8e\u5206\u6790\u67e5\u8be2\u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\u3002\u901a\u8fc7\u4f7f\u7528EXPLAIN\uff0c\u6211\u4eec\u53ef\u4ee5\u4e86\u89e3\u5230MySQL\u6570\u636e\u5e93\u662f\u5982\u4f55\u6267\u884c\u67e5\u8be2\u8bed\u53e5\u7684\uff0c\u4ece\u800c\u5e2e\u52a9\u6211\u4eec\u4f18\u5316\u67e5\u8be2\u6027\u80fd\u3002<\/p>\n<p>EXPLAIN\u7684\u57fa\u672c\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre>EXPLAIN SELECT \u5217\u540d FROM \u8868\u540d WHERE \u6761\u4ef6;<\/pre>\n<p>EXPLAIN\u7684\u8fd4\u56de\u7ed3\u679c\u5305\u542b\u4e86\u4ee5\u4e0b\u51e0\u4e2a\u91cd\u8981\u7684\u5b57\u6bb5\uff1a<\/p>\n<ul>\n<li>id\uff1a\u8868\u793a\u67e5\u8be2\u7684\u6807\u8bc6\u7b26\uff0c\u6bcf\u4e2a\u67e5\u8be2\u90fd\u6709\u4e00\u4e2a\u552f\u4e00\u7684\u6807\u8bc6\u7b26\u3002<\/li>\n<li>select_type\uff1a\u8868\u793a\u67e5\u8be2\u7684\u7c7b\u578b\uff0c\u53ef\u80fd\u7684\u53d6\u503c\u6709SIMPLE\u3001PRIMARY\u3001SUBQUERY\u3001DERIVED\u3001UNION\u3001UNION RESULT\u7b49\u3002<\/li>\n<li>table\uff1a\u8868\u793a\u67e5\u8be2\u7684\u8868\u540d\u3002<\/li>\n<li>partitions\uff1a\u8868\u793a\u67e5\u8be2\u6240\u4f7f\u7528\u7684\u5206\u533a\u3002<\/li>\n<li>type\uff1a\u8868\u793a\u8bbf\u95ee\u7c7b\u578b\uff0c\u53ef\u80fd\u7684\u53d6\u503c\u6709ALL\u3001index\u3001range\u3001ref\u3001eq_ref\u3001const\u3001system\u3001NULL\u7b49\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u8bbf\u95ee\u7c7b\u578b\u7684\u503c\u8d8a\u597d\uff0c\u67e5\u8be2\u7684\u6027\u80fd\u4e5f\u5c31\u8d8a\u597d\u3002<\/li>\n<li>possible_keys\uff1a\u8868\u793a\u53ef\u80fd\u7528\u5230\u7684\u7d22\u5f15\u3002<\/li>\n<li>key\uff1a\u8868\u793a\u5b9e\u9645\u4f7f\u7528\u7684\u7d22\u5f15\u3002<\/li>\n<li>key_len\uff1a\u8868\u793a\u7d22\u5f15\u5b57\u6bb5\u7684\u957f\u5ea6\u3002<\/li>\n<li>ref\uff1a\u8868\u793a\u7d22\u5f15\u4e4b\u95f4\u7684\u5173\u7cfb\u3002<\/li>\n<li>rows\uff1a\u8868\u793a\u626b\u63cf\u7684\u884c\u6570\u3002<\/li>\n<li>filtered\uff1a\u8868\u793a\u67e5\u8be2\u7ed3\u679c\u7684\u8fc7\u6ee4\u7a0b\u5ea6\u3002<\/li>\n<li>Extra\uff1a\u8868\u793a\u989d\u5916\u7684\u4fe1\u606f\uff0c\u6bd4\u5982\u662f\u5426\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\u3001\u4f7f\u7528\u4e86\u6587\u4ef6\u6392\u5e8f\u7b49\u3002<\/li>\n<\/ul>\n<p>\u4e0b\u9762\u662f\u4e00\u4e2a\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\uff0c\u901a\u8fc7\u5206\u6790\u548c\u4f18\u5316\u4e00\u4e2a\u67e5\u8be2\u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\u6765\u8bf4\u660e\u5982\u4f55\u4f7f\u7528EXPLAIN\u3002<\/p>\n<p>\u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a\u540d\u4e3a&#8221;orders&#8221;\u7684\u8868\uff0c\u5b58\u50a8\u4e86\u7528\u6237\u8ba2\u5355\u7684\u76f8\u5173\u4fe1\u606f\uff0c\u5305\u62ec\u8ba2\u5355ID\u3001\u7528\u6237ID\u3001\u8ba2\u5355\u91d1\u989d\u7b49\u3002<\/p>\n<p>\u6211\u4eec\u5e0c\u671b\u67e5\u8be2\u8ba2\u5355\u91d1\u989d\u5927\u4e8e1000\u7684\u8ba2\u5355\u7684\u4fe1\u606f\uff0c\u540c\u65f6\u6309\u8ba2\u5355ID\u964d\u5e8f\u6392\u5217\u3002\u67e5\u8be2\u8bed\u53e5\u5982\u4e0b\uff1a<\/p>\n<pre>SELECT * FROM orders WHERE amount &gt; 1000 ORDER BY order_id DESC;<\/pre>\n<p>\u9996\u5148\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528EXPLAIN\u6765\u5206\u6790\u8fd9\u4e2a\u67e5\u8be2\u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\u3002<\/p>\n<pre>EXPLAIN SELECT * FROM orders WHERE amount &gt; 1000 ORDER BY order_id DESC;<\/pre>\n<p>\u6267\u884cEXPLAIN\u540e\uff0cMySQL\u4f1a\u8fd4\u56de\u67e5\u8be2\u7684\u6267\u884c\u8ba1\u5212\uff0c\u6211\u4eec\u53ef\u4ee5\u6839\u636e\u8fd4\u56de\u7ed3\u679c\u6765\u4f18\u5316\u67e5\u8be2\u6027\u80fd\u3002<\/p>\n<p>\u5047\u8bbe\u8fd4\u56de\u7684\u6267\u884c\u8ba1\u5212\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<pre>id  select_type   table  type  possible_keys  key  key_len  ref  rows  Extra\n1   SIMPLE        orders range amount        NULL NULL     NULL 1000  Using where;Using filesort<\/pre>\n<p>\u4e0a\u9762\u7684\u6267\u884c\u8ba1\u5212\u4e2d\uff0c\u53ef\u4ee5\u770b\u5230type\u7684\u503c\u4e3a&#8221;range&#8221;\uff0c\u8868\u793aMySQL\u5c06\u5bf9\u8868\u4e2d\u7684\u67d0\u4e2a\u7d22\u5f15\u8fdb\u884c\u8303\u56f4\u626b\u63cf\u3002\u8fd9\u610f\u5473\u7740MySQL\u6ca1\u6709\u4f7f\u7528\u4efb\u4f55\u7d22\u5f15\u6765\u52a0\u901f\u67e5\u8be2\uff0c\u5bfc\u81f4\u67e5\u8be2\u6027\u80fd\u8f83\u5dee\u3002\u540c\u65f6\uff0cExtra\u5b57\u6bb5\u4e2d\u7684&#8221;Using filesort&#8221;\u8868\u793a\u4f7f\u7528\u4e86\u6587\u4ef6\u6392\u5e8f\uff0c\u8fd9\u4e5f\u4f1a\u5bf9\u67e5\u8be2\u6027\u80fd\u4ea7\u751f\u8d1f\u9762\u5f71\u54cd\u3002<\/p>\n<p>\u4e3a\u4e86\u4f18\u5316\u67e5\u8be2\u6027\u80fd\uff0c\u6211\u4eec\u53ef\u4ee5\u4e3a&#8221;amount&#8221;\u5b57\u6bb5\u6dfb\u52a0\u4e00\u4e2a\u7d22\u5f15\uff1a<\/p>\n<pre>ALTER TABLE orders ADD INDEX idx_amount (amount);<\/pre>\n<p>\u518d\u6b21\u6267\u884cEXPLAIN\uff0c\u6211\u4eec\u53ef\u4ee5\u770b\u5230\u6267\u884c\u8ba1\u5212\u53d1\u751f\u4e86\u53d8\u5316\uff1a<\/p>\n<pre>id  select_type   table  type   possible_keys  key       key_len  ref  rows  Extra\n1   SIMPLE        orders range  idx_amount     idx_amount 2        NULL 1000  Using where<\/pre>\n<p>\u73b0\u5728\uff0ctype\u7684\u503c\u53d8\u4e3a&#8221;range&#8221;\uff0c\u8868\u793aMySQL\u4f1a\u4f7f\u7528\u65b0\u6dfb\u52a0\u7684\u7d22\u5f15\u8fdb\u884c\u8303\u56f4\u626b\u63cf\u3002\u540c\u65f6\uff0cExtra\u5b57\u6bb5\u4e2d\u6ca1\u6709&#8221;Using filesort&#8221;\u7684\u63d0\u793a\uff0c\u8bf4\u660e\u67e5\u8be2\u7684\u6027\u80fd\u5f97\u5230\u4e86\u663e\u8457\u63d0\u5347\u3002<\/p>\n<p>\u901a\u8fc7\u4ee5\u4e0a\u7684\u793a\u4f8b\uff0c\u6211\u4eec\u53ef\u4ee5\u770b\u5230EXPLAIN\u7684\u4f7f\u7528\u65b9\u6cd5\u53ca\u5176\u91cd\u8981\u6027\u3002\u901a\u8fc7\u5206\u6790\u6267\u884c\u8ba1\u5212\uff0c\u6211\u4eec\u53ef\u4ee5\u627e\u5230\u5f71\u54cd\u67e5\u8be2\u6027\u80fd\u7684\u74f6\u9888\uff0c\u5e76\u91c7\u53d6\u76f8\u5e94\u7684\u4f18\u5316\u63aa\u65bd\uff0c\u63d0\u5347\u6570\u636e\u5e93\u7684\u67e5\u8be2\u6548\u7387\u3002<\/p>\n<p>\u603b\u7ed3\u8d77\u6765\uff0c\u4f7f\u7528EXPLAIN\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u6df1\u5165\u4e86\u89e3MySQL\u6570\u636e\u5e93\u7684\u67e5\u8be2\u6267\u884c\u8fc7\u7a0b\uff0c\u5e76\u627e\u51fa\u4f18\u5316\u67e5\u8be2\u6027\u80fd\u7684\u65b9\u6cd5\u3002\u901a\u8fc7\u5206\u6790\u6267\u884c\u8ba1\u5212\uff0c\u6211\u4eec\u53ef\u4ee5\u5224\u65ad\u662f\u5426\u9700\u8981\u6dfb\u52a0\u7d22\u5f15\u3001\u6539\u53d8\u67e5\u8be2\u8bed\u53e5\u7684\u987a\u5e8f\u7b49\u3002\u5728\u5b9e\u9645\u7684\u5f00\u53d1\u8fc7\u7a0b\u4e2d\uff0c\u5408\u7406\u4f7f\u7528EXPLAIN\u5de5\u5177\u662f\u63d0\u5347\u6570\u636e\u5e93\u6027\u80fd\u7684\u91cd\u8981\u73af\u8282\u4e4b\u4e00\u3002<\/p>\n<p>\u672c\u7bc7\u5173\u4e8e\u300a\u4f7f\u7528MySQL\u7684EXPLAIN\u8bed\u53e5\u8fdb\u884c\u6027\u80fd\u4f18\u5316\u300b\u7684\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\u5566\uff0c\u4f46\u662f\u5b66\u65e0\u6b62\u5883\uff0c\u60f3\u8981\u4e86\u89e3\u5b66\u4e60\u66f4\u591a\u5173\u4e8e\u6570\u636e\u5e93\u7684\u76f8\u5173\u77e5\u8bc6\uff0c\u8bf7\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>\u4f7f\u7528MySQL\u7684EXPLAIN\u8bed&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-199677","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199677","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=199677"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199677\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199677"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199677"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199677"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}