{"id":481,"date":"2021-09-11T00:36:07","date_gmt":"2021-09-10T16:36:07","guid":{"rendered":"http:\/\/dba.qishuo.xin\/?p=481"},"modified":"2021-09-11T00:36:40","modified_gmt":"2021-09-10T16:36:40","slug":"mariadb%e4%b8%adexplain%e6%89%a7%e8%a1%8c%e8%ae%a1%e5%88%92%e7%9a%84%e5%90%84%e5%b1%9e%e6%80%a7%e5%90%ab%e4%b9%89","status":"publish","type":"post","link":"http:\/\/dba.qishuo.xin\/?p=481","title":{"rendered":"MariaDB\u4e2dexplain\u6267\u884c\u8ba1\u5212\u7684\u5404\u5c5e\u6027\u542b\u4e49"},"content":{"rendered":"<p>\u5982\u679c\u80fd\u641e\u6e05\u695aMySQL\u662f\u5982\u4f55\u4f18\u5316\u548c\u6267\u884c\u67e5\u8be2\u7684\uff0c\u5bf9\u4f18\u5316\u67e5\u8be2\u4e00\u5b9a\u4f1a\u6709\u5e2e\u52a9\u3002\u5f88\u591a\u67e5\u8be2\u4f18\u5316\u5b9e\u9645\u4e0a\u5c31\u662f\u9075\u5faa\u4e00\u4e9b\u539f\u5219\u8ba9\u4f18\u5316\u5668\u80fd\u591f\u6309\u671f\u671b\u7684\u5408\u7406\u7684\u65b9\u5f0f\u8fd0\u884c\u3002<\/p>\n<p>\u4e0b\u56fe\u662fMySQL\u6267\u884c\u4e00\u4e2a\u67e5\u8be2\u7684\u8fc7\u7a0b\u3002\u5b9e\u9645\u4e0a\u6bcf\u4e00\u6b65\u90fd\u6bd4\u60f3\u8c61\u4e2d\u7684\u590d\u6742\uff0c\u5c24\u5176\u4f18\u5316\u5668\uff0c\u66f4\u590d\u6742\u4e5f\u66f4\u96be\u7406\u89e3\u3002\u672c\u6587\u53ea\u7ed9\u4e88\u7b80\u5355\u7684\u4ecb\u7ecd\u3002<br \/>\n<a href=\"http:\/\/dba.qishuo.xin\/wp-content\/uploads\/2021\/09\/wp_editor_md_f0b491fbced56e66378417cf08c3d2c7.jpg\" data-fancybox=\"images\" data-fancybox=\"images\"><img decoding=\"async\" src=\"http:\/\/dba.qishuo.xin\/wp-content\/uploads\/2021\/09\/wp_editor_md_f0b491fbced56e66378417cf08c3d2c7.jpg\" alt=\"\" \/><\/a><\/p>\n<p>MySQL\u67e5\u8be2\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n<p>1.\u5ba2\u6237\u7aef\u5c06\u67e5\u8be2\u53d1\u9001\u5230MySQL\u670d\u52a1\u5668\uff1b<\/p>\n<p>2.\u670d\u52a1\u5668\u5148\u68c0\u67e5\u67e5\u8be2\u7f13\u5b58\uff0c\u5982\u679c\u547d\u4e2d\uff0c\u7acb\u5373\u8fd4\u56de\u7f13\u5b58\u4e2d\u7684\u7ed3\u679c\uff1b\u5426\u5219\u8fdb\u5165\u4e0b\u4e00\u9636\u6bb5\uff1b<\/p>\n<p>3.\u670d\u52a1\u5668\u5bf9SQL\u8fdb\u884c\u89e3\u6790\u3001\u9884\u5904\u7406\uff0c\u518d\u7531\u4f18\u5316\u5668\u751f\u6210\u5bf9\u8c61\u7684\u6267\u884c\u8ba1\u5212\uff1b<\/p>\n<p>4.MySQL\u6839\u636e\u4f18\u5316\u5668\u751f\u6210\u7684\u6267\u884c\u8ba1\u5212\uff0c\u8c03\u7528\u5b58\u50a8\u5f15\u64ceAPI\u6765\u6267\u884c\u67e5\u8be2\uff1b<\/p>\n<p>5.\u670d\u52a1\u5668\u5c06\u7ed3\u679c\u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\uff0c\u540c\u65f6\u7f13\u5b58\u67e5\u8be2\u7ed3\u679c\uff1b<\/p>\n<p><a href=\"http:\/\/dba.qishuo.xin\/wp-content\/uploads\/2021\/09\/wp_editor_md_fa5be4e4f56244f646ac803d1b3d3597.jpg\" data-fancybox=\"images\" data-fancybox=\"images\"><img decoding=\"async\" src=\"http:\/\/dba.qishuo.xin\/wp-content\/uploads\/2021\/09\/wp_editor_md_fa5be4e4f56244f646ac803d1b3d3597.jpg\" alt=\"\" \/><\/a><\/p>\n<p><strong>\u5404\u5c5e\u6027\u542b\u4e49\uff1a<\/strong><br \/>\n<strong>id<\/strong>\uff1a<br \/>\nselect\u67e5\u8be2\u5e8f\u5217\u53f7\uff0cid\u76f8\u540c\uff0c\u6267\u884c\u987a\u5e8f\u7531\u4e0a\u81f3\u4e0b\uff1bid\u4e0d\u540c\uff0cid\u503c\u8d8a\u5927\u4f18\u5148\u7ea7\u8d8a\u9ad8\uff0c\u8d8a\u5148\u88ab\u6267\u884c\u3002<\/p>\n<p><strong>select_type<\/strong>\uff1a\u67e5\u8be2\u7684\u7c7b\u578b\uff0c\u4e3b\u8981\u662f\u533a\u522b\u666e\u901a\u67e5\u8be2\u548c\u8054\u5408\u67e5\u8be2\u3001\u5b50\u67e5\u8be2\u4e4b\u7c7b\u7684\u590d\u6742\u67e5\u8be2<\/p>\n<ul>\n<li>SIMPLE\uff1a\u67e5\u8be2\u4e2d\u4e0d\u5305\u542b\u5b50\u67e5\u8be2\u6216\u8005UNION<\/li>\n<li>\u67e5\u8be2\u4e2d\u82e5\u5305\u542b\u4efb\u4f55\u590d\u6742\u7684\u5b50\u90e8\u5206\uff0c\u6700\u5916\u5c42\u67e5\u8be2\u5219\u88ab\u6807\u8bb0\u4e3a\uff1aPRIMARY<\/li>\n<li>\u5728SELECT\u6216WHERE\u5217\u8868\u4e2d\u5305\u542b\u4e86\u5b50\u67e5\u8be2\uff0c\u8be5\u5b50\u67e5\u8be2\u88ab\u6807\u8bb0\u4e3a\uff1aSUBQUERY<\/li>\n<li>DERIVED\uff1a\u5728from\u5217\u8868\u4e2d\u5305\u542b\u7684\u5b50\u67e5\u8be2\u88ab\u6807\u8bb0\u4e3aderived(\u884d\u751f)\uff0cmysql\u6216\u9012\u5f52\u6267\u884c\u8fd9\u4e9b\u5b50\u67e5\u8be2\uff0c\u628a\u7ed3\u679c\u653e\u5728\u96f6\u65f6\u8868\u91cc\u3002<\/li>\n<li>UNION\uff1a\u82e5\u7b2c\u4e8c\u4e2aselect\u51fa\u73b0\u5728union\u4e4b\u540e\uff0c\u5219\u88ab\u6807\u8bb0\u4e3aunion\uff1b\u82e5union\u5305\u542b\u5728from\u5b50\u53e5\u7684\u5b50\u67e5\u8be2\u4e2d\uff0c\u5916\u5c42select\u5c06\u88ab\u6807\u8bb0\u4e3aderived\u3002<\/li>\n<li>UNION RESULT\uff1a\u4eceunion\u8868\u83b7\u53d6\u7ed3\u679c\u7684select\u3002<\/li>\n<\/ul>\n<p><strong>table<\/strong>\uff1a\u8f93\u51fa\u7684\u884c\u6240\u5f15\u7528\u7684\u8868<\/p>\n<p><strong>type<\/strong>\uff1a\u8bbf\u95ee\u7c7b\u578b<\/p>\n<p><a href=\"http:\/\/dba.qishuo.xin\/wp-content\/uploads\/2021\/09\/wp_editor_md_b989c893f5837ec47b59bc1137f70b4e.jpg\" data-fancybox=\"images\" data-fancybox=\"images\"><img decoding=\"async\" src=\"http:\/\/dba.qishuo.xin\/wp-content\/uploads\/2021\/09\/wp_editor_md_b989c893f5837ec47b59bc1137f70b4e.jpg\" alt=\"\" \/><\/a><\/p>\n<p>\u4ece\u5de6\u81f3\u53f3\uff0c\u6027\u80fd\u7531\u5dee\u5230\u597d<\/p>\n<ul>\n<li>ALL\uff1a\u626b\u63cf\u5168\u8868<\/li>\n<li>index\uff1a\u626b\u63cf\u5168\u90e8\u7d22\u5f15\u6811<\/li>\n<li>range\uff1a\u626b\u63cf\u90e8\u5206\u7d22\u5f15\uff0c\u7d22\u5f15\u8303\u56f4\u626b\u63cf\uff0c\u5bf9\u7d22\u5f15\u7684\u626b\u63cf\u5f00\u59cb\u4e8e\u67d0\u4e00\u70b9\uff0c\u8fd4\u56de\u5339\u914d\u503c\u57df\u7684\u884c\uff0c\u5e38\u89c1\u4e8ebetween\u3001&lt;\u3001>\u7b49\u7684\u67e5\u8be2<\/li>\n<li>ref\uff1a\u4f7f\u7528\u975e\u552f\u4e00\u7d22\u5f15\u6216\u975e\u552f\u4e00\u7d22\u5f15\u524d\u7f00\u8fdb\u884c\u7684\u67e5\u627e<\/li>\n<li>eq_ref\uff1a\u552f\u4e00\u6027\u7d22\u5f15\u626b\u63cf\uff0c\u5bf9\u4e8e\u6bcf\u4e2a\u7d22\u5f15\u952e\uff0c\u8868\u4e2d\u53ea\u6709\u4e00\u6761\u8bb0\u5f55\u4e0e\u4e4b\u5339\u914d\u3002\u5e38\u89c1\u4e8e\u4e3b\u952e\u6216\u552f\u4e00\u7d22\u5f15\u626b\u63cf<\/li>\n<li>const\uff1a\u5355\u8868\u4e2d\u6700\u591a\u6709\u4e00\u4e2a\u5339\u914d\u884c\uff0c\u67e5\u8be2\u8d77\u6765\u975e\u5e38\u8fc5\u901f\uff0c\u4f8b\u5982\u6839\u636e\u4e3b\u952e\u6216\u552f\u4e00\u7d22\u5f15\u67e5\u8be2\u3002<\/li>\n<li>system\uff1asystem\u662fconst\u7c7b\u578b\u7684\u7279\u4f8b\uff0c\u5f53\u67e5\u8be2\u7684\u8868\u53ea\u6709\u4e00\u884c\u7684\u60c5\u51b5\u4e0b\uff0c \u4f7f\u7528system\u3002<\/li>\n<li>NULL\uff1a\u4e0d\u7528\u8bbf\u95ee\u8868\u6216\u8005\u7d22\u5f15\uff0c\u76f4\u63a5\u5c31\u80fd\u5f97\u5230\u7ed3\u679c\uff0c\u5982select 1 from test where 1<\/li>\n<\/ul>\n<p><strong>possible_keys<\/strong>\uff1a\u8868\u793a\u67e5\u8be2\u65f6\u53ef\u80fd\u4f7f\u7528\u7684\u7d22\u5f15\u3002\u5982\u679c\u662f\u7a7a\u7684\uff0c\u6ca1\u6709\u76f8\u5173\u7684\u7d22\u5f15\u3002\u8fd9\u65f6\u8981\u63d0\u9ad8\u6027\u80fd\uff0c\u53ef\u901a\u8fc7\u68c0\u9a8cWHERE\u5b50\u53e5\uff0c\u770b\u662f\u5426\u5f15\u7528\u67d0\u4e9b\u5b57\u6bb5\uff0c\u6216\u8005\u68c0\u67e5\u5b57\u6bb5\u4e0d\u662f\u9002\u5408\u7d22\u5f15\u3002\uff08\u4f46\u4e0d\u4e00\u5b9a\u88ab\u67e5\u8be2\u5b9e\u9645\u4f7f\u7528\uff09<\/p>\n<p><strong>key<\/strong>\uff1a\u663e\u793aMySQL\u5b9e\u9645\u51b3\u5b9a\u4f7f\u7528\u7684\u7d22\u5f15\u3002\u5982\u679c\u6ca1\u6709\u7d22\u5f15\u88ab\u9009\u62e9\uff0c\u662fNULL<\/p>\n<p><strong>key_len<\/strong>\uff1a\u4f7f\u7528\u5230\u7d22\u5f15\u5b57\u6bb5\u7684\u957f\u5ea6<br \/>\n\u6ce8\uff1akey_len\u663e\u793a\u7684\u503c\u4e3a\u7d22\u5f15\u5b57\u6bb5\u7684\u6700\u5927\u53ef\u80fd\u957f\u5ea6\uff0c\u5e76\u975e\u5b9e\u9645\u4f7f\u7528\u957f\u5ea6\uff0c\u5373key_len\u662f\u6839\u636e\u8868\u5b9a\u4e49\u8ba1\u7b97\u800c\u5f97\uff0c\u4e0d\u662f\u901a\u8fc7\u8868\u5185\u68c0\u7d22\u51fa\u7684\u3002\uff08\u8868\u793a\u7d22\u5f15\u4e2d\u4f7f\u7528\u7684\u5b57\u8282\u6570\uff0c\u901a\u8fc7\u8be5\u5217\u8ba1\u7b97\u67e5\u8be2\u4e2d\u4f7f\u7528\u7684\u7d22\u5f15\u7684\u957f\u5ea6\u3002\u5728\u4e0d\u635f\u5931\u7cbe\u786e\u6027\u7684\u60c5\u51b5\u4e0b\uff0c\u957f\u5ea6\u8d8a\u77ed\u8d8a\u597d\u663e\u793a\u7684\u662f\u7d22\u5f15\u5b57\u6bb5\u7684\u6700\u5927\u957f\u5ea6\uff0c\u5e76\u975e\u5b9e\u9645\u4f7f\u7528\u957f\u5ea6\uff09<\/p>\n<p><strong>ref<\/strong>\uff1a\u663e\u793a\u54ea\u4e2a\u5b57\u6bb5\u6216\u5e38\u6570\u4e0ekey\u4e00\u8d77\u88ab\u4f7f\u7528<\/p>\n<p><strong>rows<\/strong>\uff1a\u8fd9\u4e2a\u6570\u8868\u793amysql\u8981\u904d\u5386\u591a\u5c11\u6570\u636e\u624d\u80fd\u627e\u5230\uff0c\u8868\u793aMySQL\u6839\u636e\u8868\u7edf\u8ba1\u4fe1\u606f\u53ca\u7d22\u5f15\u9009\u7528\u60c5\u51b5\uff0c\u4f30\u7b97\u7684\u627e\u5230\u6240\u9700\u7684\u8bb0\u5f55\u6240\u9700\u8981\u8bfb\u53d6\u7684\u884c\u6570\uff0c\u5728innodb\u4e0a\u53ef\u80fd\u662f\u4e0d\u51c6\u786e\u7684\u3002<\/p>\n<p><strong>filtered<\/strong>:<br \/>\n\u8fd4\u56de\u7ed3\u679c\u7684\u884c\u6570\u5360\u8bfb\u53d6\u884c\u6570\u7684\u767e\u5206\u6bd4\uff0c\u503c\u8d8a\u5927\u8d8a\u597d\uff1b<\/p>\n<p><strong>Extra<\/strong>\uff1a\u6267\u884c\u60c5\u51b5\u7684\u8bf4\u660e\u548c\u63cf\u8ff0\u3002\u5305\u542b\u4e0d\u9002\u5408\u5728\u5176\u4ed6\u5217\u4e2d\u663e\u793a\u4f46\u5341\u5206\u91cd\u8981\u7684\u989d\u5916\u4fe1\u606f\u3002<\/p>\n<ul>\n<li>Distinct\uff1a\u4e00\u65e6mysql\u627e\u5230\u4e86\u4e0e\u884c\u76f8\u8054\u5408\u5339\u914d\u7684\u884c\uff0c\u5c31\u4e0d\u518d\u641c\u7d22\u4e86\u3002<\/li>\n<li>Using filesort \uff1amysql\u5bf9\u6570\u636e\u4f7f\u7528\u4e00\u4e2a\u5916\u90e8\u7684\u7d22\u5f15\u6392\u5e8f\uff0c\u800c\u4e0d\u662f\u6309\u7167\u8868\u5185\u7684\u7d22\u5f15\u8fdb\u884c\u6392\u5e8f\u8bfb\u53d6\u3002\u4e5f\u5c31\u662f\u8bf4mysql\u65e0\u6cd5\u5229\u7528\u7d22\u5f15\u5b8c\u6210\u7684\u6392\u5e8f\u64cd\u4f5c\u6210\u4e3a\u201c\u6587\u4ef6\u6392\u5e8f\u201d \u3002<\/li>\n<li>Using index \uff1a\u8868\u793a\u4f7f\u7528\u7d22\u5f15\uff0c\u5982\u679c\u53ea\u6709 Using index\uff0c\u8bf4\u660e\u4ed6\u6ca1\u6709\u67e5\u8be2\u5230\u6570\u636e\u8868\uff0c\u53ea\u7528\u7d22\u5f15\u8868\u5c31\u5b8c\u6210\u4e86\u8fd9\u4e2a\u67e5\u8be2\uff0c\u8fd9\u4e2a\u53eb\u8986\u76d6\u7d22\u5f15\u3002\u5373\u5217\u6570\u636e\u662f\u4ece\u4ec5\u4ec5\u4f7f\u7528\u4e86\u7d22\u5f15\u4e2d\u7684\u4fe1\u606f\u800c\u6ca1\u6709\u8bfb\u53d6\u5b9e\u9645\u7684\u884c\u52a8\u7684\u8868\u8fd4\u56de\u7684\uff0c\u8fd9\u53d1\u751f\u5728\u5bf9\u8868\u7684\u5168\u90e8\u7684\u8bf7\u6c42\u5217\u90fd\u662f\u540c\u4e00\u4e2a\u7d22\u5f15\u7684\u90e8\u5206\u7684\u65f6\u5019\u3002<\/li>\n<li>Using temporary \uff1a\u4f7f\u7528\u4e34\u65f6\u8868\u4fdd\u5b58\u4e2d\u95f4\u7ed3\u679c\uff0c\u4e5f\u5c31\u662f\u8bf4mysql\u5728\u5bf9\u67e5\u8be2\u7ed3\u679c\u6392\u5e8f\u65f6\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\uff0c\u5e38\u89c1\u4e8eorder by \u548c group by\u3002<\/li>\n<li>Using where \uff1a\u4f7f\u7528\u4e86where\u8fc7\u6ee4\u3002\u8868\u793a\u6761\u4ef6\u67e5\u8be2\uff0c\u5982\u679c\u4e0d\u8bfb\u53d6\u8868\u7684\u6240\u6709\u6570\u636e\uff0c\u6216\u4e0d\u662f\u4ec5\u4ec5\u901a\u8fc7\u7d22\u5f15\u5c31\u53ef\u4ee5\u83b7\u53d6\u6240\u6709\u9700\u8981\u7684\u6570\u636e\uff0c\u5219\u4f1a\u51fa\u73b0 Using where\u3002<\/li>\n<li>Using join buffer \uff1a\u4f7f\u7528\u4e86\u94fe\u63a5\u7f13\u5b58\u3002<\/li>\n<li>select tables optimized away\uff1a \u5728\u6ca1\u6709group by\u5b50\u53e5\u7684\u60c5\u51b5\u4e0b\uff0c\u57fa\u4e8e\u7d22\u5f15\u4f18\u5316MIN\/MAX\u64cd\u4f5c\u6216\u8005\u5bf9\u4e8eMyISAM\u5b58\u50a8\u5f15\u64ce\u4f18\u5316COUNT\u64cd\u4f5c\uff0c\u4e0d\u5fc5\u7b49\u5230\u6267\u884c\u9636\u6bb5\u5728\u8fdb\u884c\u8ba1\u7b97\uff0c\u67e5\u8be2\u6267\u884c\u8ba1\u5212\u751f\u6210\u7684\u9636\u6bb5\u5373\u53ef\u5b8c\u6210\u4f18\u5316\u3002<\/li>\n<\/ul>\n<p>\u53c2\u8003\uff1a<a target=\"_blank\" class=\"wp-editor-md-post-content-link\" href=\"https:\/\/www.cnblogs.com\/ggjucheng\/archive\/2012\/11\/11\/2765237.html\">https:\/\/www.cnblogs.com\/ggjucheng\/archive\/2012\/11\/11\/2765237.html<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5982\u679c\u80fd\u641e\u6e05\u695aMySQL\u662f\u5982\u4f55\u4f18\u5316\u548c\u6267\u884c\u67e5\u8be2\u7684\uff0c\u5bf9\u4f18&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,3],"tags":[61,12,62],"class_list":["post-481","post","type-post","status-publish","format-standard","hentry","category-mariadb","category-mariadbmysql","tag-explain","tag-mariadb","tag-62"],"_links":{"self":[{"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=\/wp\/v2\/posts\/481","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=481"}],"version-history":[{"count":2,"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=\/wp\/v2\/posts\/481\/revisions"}],"predecessor-version":[{"id":483,"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=\/wp\/v2\/posts\/481\/revisions\/483"}],"wp:attachment":[{"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=481"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=481"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/dba.qishuo.xin\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}