{"id":7037,"date":"2024-11-14T08:16:56","date_gmt":"2024-11-14T00:16:56","guid":{"rendered":"https:\/\/fwq.ai\/blog\/7037\/"},"modified":"2024-11-14T08:16:56","modified_gmt":"2024-11-14T00:16:56","slug":"%e8%81%94%e5%90%88%e7%b4%a2%e5%bc%95%e6%9f%a5%e8%af%a2%e6%95%88%e7%8e%87%e5%af%b9%e6%af%94%ef%bc%9a%e5%a6%82%e4%bd%95%e5%88%a4%e6%96%ad%e6%9c%80%e6%85%a2%e7%9a%84%e6%9f%a5%e8%af%a2%e4%bb%a5%e5%8f%8a","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/7037\/","title":{"rendered":"\u8054\u5408\u7d22\u5f15\u67e5\u8be2\u6548\u7387\u5bf9\u6bd4\uff1a\u5982\u4f55\u5224\u65ad\u6700\u6162\u7684\u67e5\u8be2\u4ee5\u53ca\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5\uff1f"},"content":{"rendered":"<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/001\/246\/273\/173034234430739.jpg\" class=\"aligncenter\" title=\"\u8054\u5408\u7d22\u5f15\u67e5\u8be2\u6548\u7387\u5bf9\u6bd4\uff1a\u5982\u4f55\u5224\u65ad\u6700\u6162\u7684\u67e5\u8be2\u4ee5\u53ca\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5\uff1f\u63d2\u56fe\" alt=\"\u8054\u5408\u7d22\u5f15\u67e5\u8be2\u6548\u7387\u5bf9\u6bd4\uff1a\u5982\u4f55\u5224\u65ad\u6700\u6162\u7684\u67e5\u8be2\u4ee5\u53ca\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5\uff1f\u63d2\u56fe\" \/><\/p>\n<p><strong>\u4f18\u5316\u8054\u5408\u7d22\u5f15\u67e5\u8be2\uff1a\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5<\/strong><\/p>\n<p>\u95ee\u9898\uff1a\u5df2\u5728 test \u8868\u4e0a\u521b\u5efa\u4e86\u5305\u542b\u5b57\u6bb5 a\u3001b\u3001c \u7684\u8054\u5408\u7d22\u5f15 a_b_c\u3002\u9700\u8981\u7504\u522b\u4ee5\u4e0b\u67e5\u8be2\u4e2d\uff0c\u54ea\u4e00\u4e2a\u6548\u7387\u6700\u4f4e\uff1a<\/p>\n<ul>\n<li>a. select * from test where a = 10 and b &gt; 50<\/li>\n<li>b. select * from test where a = 10 and b &gt; 10 order by c<\/li>\n<li>c. select * from test where a = 10 and b = 10 order by a<\/li>\n<li>d. select * from test where a = 10 and b = 10 order by c<\/li>\n<\/ul>\n<p>\u6b64\u5916\uff0c\u5982\u4f55\u67e5\u770b\u8054\u5408\u7d22\u5f15\u4e2d\u547d\u4e2d\u7684\u5b57\u6bb5\uff1f<\/p>\n<p>\u89e3\u7b54\uff1a<\/p>\n<p><strong>\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5<\/strong><\/p>\n<p>\u8981\u67e5\u770b\u8054\u5408\u7d22\u5f15\u547d\u4e2d\u5b57\u6bb5\uff0c\u53ef\u4ee5\u4f7f\u7528  \u7684 expln \u547d\u4ee4\u8f93\u51fa\u6267\u884c\u8ba1\u5212\uff1a<\/p>\n<pre>EXPLAIN SELECT * FROM test WHERE a = 10 AND b &gt; 50;<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>\u67e5\u8be2\u8f93\u51fa\u5b57\u6bb5\u542b\u4e49\uff1a<\/strong><\/p>\n<ul>\n<li> <strong>id\uff1a<\/strong> \u67e5\u8be2\u7684\u5185\u90e8id\u53f7\u3002<\/li>\n<li> <strong>select_type\uff1a<\/strong> \u67e5\u8be2\u7c7b\u578b\uff08\u5982 simple\u3001primary\uff09\u3002<\/li>\n<li> <strong>table\uff1a<\/strong> \u6d89\u53ca\u7684\u8868\u540d\u3002<\/li>\n<li> <strong>partitions\uff1a<\/strong> \u67e5\u8be2\u662f\u5426\u4f7f\u7528\u4e86\u5206\u533a\u529f\u80fd\u3002<\/li>\n<li> <strong>type\uff1a<\/strong> \u8bbf\u95ee\u7c7b\u578b\uff08\u5982 all\u3001index\u3001range\uff09\u3002<\/li>\n<li> <strong>possible_keys\uff1a<\/strong> \u53ef\u80fd\u4f7f\u7528\u7684\u7d22\u5f15\u3002<\/li>\n<li> <strong>key\uff1a<\/strong> \u5b9e\u9645\u4f7f\u7528\u7684\u7d22\u5f15\u3002<\/li>\n<li> <strong>key_len\uff1a<\/strong> \u4f7f\u7528\u7d22\u5f15\u5b57\u6bb5\u7684\u957f\u5ea6\u3002<\/li>\n<li> <strong>ref\uff1a<\/strong> \u5f15\u7528\u7d22\u5f15\u5b57\u6bb5\u7684\u5217\u4fe1\u606f\u3002<\/li>\n<li> <strong>rows\uff1a<\/strong> \u4f30\u8ba1\u626b\u63cf\u7684\u884c\u6570\u3002<\/li>\n<li> <strong>extra\uff1a<\/strong> \u5176\u4ed6\u4fe1\u606f\uff0c\u4f8b\u5982\u8054\u5408\u7d22\u5f15\u4f7f\u7528\u7684\u5b57\u6bb5\u3002<\/li>\n<\/ul>\n<p><strong>\u6548\u7387\u6700\u4f4e\u7684\u67e5\u8be2<\/strong><\/p>\n<p>\u6839\u636e explain \u7ed3\u679c\u4e2d type \u5b57\u6bb5\u7684\u503c\uff0c\u53ef\u4ee5\u5224\u65ad\u54ea\u4e2a\u67e5\u8be2\u6548\u7387\u6700\u4f4e\uff1a<\/p>\n<ul>\n<li>all \u8868\u793a\u5168\u8868\u626b\u63cf\uff0c\u6548\u7387\u6700\u4f4e\u3002<\/li>\n<li>index \u8868\u793a\u7d22\u5f15\u626b\u63cf\uff0c\u6548\u7387\u66f4\u9ad8\u3002<\/li>\n<li>range \u8868\u793a\u8303\u56f4\u626b\u63cf\uff0c\u4ecb\u4e8e\u524d\u4e24\u8005\u4e4b\u95f4\u3002<\/li>\n<\/ul>\n<p><strong>\u547d\u4e2d\u5b57\u6bb5<\/strong><\/p>\n<p>\u5728 extra \u8f93\u51fa\u4e2d\uff0c\u4f1a\u5305\u542b\u4ee5\u4e0b\u76f8\u5173\u4fe1\u606f\uff1a<\/p>\n<ul>\n<li>using index condition \u8868\u793a\u81f3\u5c11\u4f7f\u7528\u4e86\u8054\u5408\u7d22\u5f15\u4e2d\u7684\u4e00\u4e2a\u5b57\u6bb5\u3002<\/li>\n<li>using index \u8868\u793a\u4f7f\u7528\u4e86\u8054\u5408\u7d22\u5f15\u4e2d\u7684\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li>using where \u8868\u793a\u672a\u4f7f\u7528\u7d22\u5f15\uff0c\u6539\u4e3a\u4f7f\u7528 where \u5b50\u53e5\u3002<\/li>\n<li>using join buffer \u6216 using temporary \u8868\u793a\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\u6216\u7f13\u51b2\u533a\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0a\u5c31\u662f\u8054\u5408\u7d22\u5f15\u67e5\u8be2\u6548\u7387\u5bf9\u6bd4\uff1a\u5982\u4f55\u5224\u65ad\u6700\u6162\u7684\u67e5\u8be2\u4ee5\u53ca\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4f18\u5316\u8054\u5408\u7d22\u5f15\u67e5\u8be2\uff1a\u67e5\u770b\u547d\u4e2d\u5b57\u6bb5 \u95ee\u9898\uff1a\u5df2\u5728 test \u8868\u4e0a\u521b\u5efa\u4e86\u5305\u542b\u5b57\u6bb5 a\u3001b\u3001c \u7684\u8054\u5408\u7d22\u5f15 a_b_c\u3002\u9700\u8981\u7504\u522b\u4ee5\u4e0b\u67e5\u8be2\u4e2d\uff0c\u54ea\u4e00\u4e2a\u6548\u7387\u6700\u4f4e\uff1a a. select * from test where a = 10 and b &gt; 50 b. select * from test where a = 10 and b &gt; 10 order by c c. select * from test where a = 10 and b = 10 order by a d. select * [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-7037","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/7037","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=7037"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/7037\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=7037"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=7037"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=7037"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}