{"id":7962,"date":"2024-11-14T15:34:09","date_gmt":"2024-11-14T07:34:09","guid":{"rendered":"https:\/\/fwq.ai\/blog\/7962\/"},"modified":"2024-11-14T15:34:09","modified_gmt":"2024-11-14T07:34:09","slug":"explain-%e5%88%86%e6%9e%90%e7%bb%93%e6%9e%9c%e6%98%be%e7%a4%bausing-where%ef%bc%8c%e8%bf%99%e6%98%af%e5%90%a6%e6%84%8f%e5%91%b3%e7%9d%80%e6%9f%a5%e8%af%a2%e5%ad%98%e5%9c%a8%e5%9b%9e","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/7962\/","title":{"rendered":"Explain \u5206\u6790\u7ed3\u679c\u663e\u793a\u201cUsing where\u201d\uff0c\u8fd9\u662f\u5426\u610f\u5473\u7740\u67e5\u8be2\u5b58\u5728\u56de\u8868\u64cd\u4f5c\uff1f"},"content":{"rendered":"<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/001\/246\/273\/173138166387651.jpg\" class=\"aligncenter\" title=\"Explain \u5206\u6790\u7ed3\u679c\u663e\u793a\u201cUsing where\u201d\uff0c\u8fd9\u662f\u5426\u610f\u5473\u7740\u67e5\u8be2\u5b58\u5728\u56de\u8868\u64cd\u4f5c\uff1f\u63d2\u56fe\" alt=\"Explain \u5206\u6790\u7ed3\u679c\u663e\u793a\u201cUsing where\u201d\uff0c\u8fd9\u662f\u5426\u610f\u5473\u7740\u67e5\u8be2\u5b58\u5728\u56de\u8868\u64cd\u4f5c\uff1f\u63d2\u56fe\" \/><\/p>\n<p><strong>\u5224\u65ad\u56de\u8868\u64cd\u4f5c\uff1aexpln \u5206\u6790<\/strong><\/p>\n<p>\u6839\u636e\u4f60\u7684\u95ee\u9898\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7 explain \u7684 extra \u5b57\u6bb5\u6765\u5224\u65ad\u67e5\u8be2\u662f\u5426\u5b58\u5728\u56de\u8868\u64cd\u4f5c\u3002<\/p>\n<p><strong>extra \u5b57\u6bb5\u89e3\u91ca\uff1a<\/strong><\/p>\n<ul>\n<li> <strong>using index\uff1a<\/strong>\u4f7f\u7528\u7d22\u5f15\u8986\u76d6\uff0c\u67e5\u8be2\u5b57\u6bb5\u5168\u90e8\u5728\u7d22\u5f15\u4e2d\uff0c\u4e0d\u9700\u8981\u56de\u8868\u3002<\/li>\n<li> <strong>using index condition\uff1a<\/strong>\u4f7f\u7528\u7d22\u5f15\u67e5\u627e\uff0c\u4f46\u9700\u8981\u6839\u636e\u8fc7\u6ee4\u6761\u4ef6\u5224\u65ad\uff0c\u4e5f\u4e0d\u9700\u8981\u56de\u8868\u3002<\/li>\n<li> <strong>using index with where:<\/strong> \u4f7f\u7528\u7d22\u5f15\uff0c\u4f46\u9700\u8981\u6839\u636e where \u6761\u4ef6\u8fc7\u6ee4\uff0c\u9700\u8981\u56de\u8868\u3002<\/li>\n<\/ul>\n<p><strong>\u6848\u4f8b\u5206\u6790\uff1a<\/strong><\/p>\n<p>\u4f60\u63d0\u4f9b\u7684 explain \u8f93\u51fa\u4e2d\uff0cextra \u4e3a\uff1a<\/p>\n<pre>Using where; Using index; Using temporary; Using filesort<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p>\u7531\u4e8e extra \u4e2d\u5305\u542b &#8220;using where&#8221;\uff0c\u8fd9\u610f\u5473\u7740\u67e5\u8be2\u9700\u8981\u56de\u8868\u64cd\u4f5c\u3002<\/p>\n<p><strong>\u7ed3\u8bba\uff1a<\/strong><\/p>\n<p>\u56e0\u6b64\uff0c\u6839\u636e explain \u5206\u6790\u7684\u7ed3\u679c\uff0c\u4f60\u7684\u67e5\u8be2\u8fd8\u5b58\u5728\u56de\u8868\u64cd\u4f5c\u3002<\/p>\n<p>\u4ee5\u4e0a\u5c31\u662fExpln \u5206\u6790\u7ed3\u679c\u663e\u793a\u201cUsing where\u201d\uff0c\u8fd9\u662f\u5426\u610f\u5473\u7740\u67e5\u8be2\u5b58\u5728\u56de\u8868\u64cd\u4f5c\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>\u5224\u65ad\u56de\u8868\u64cd\u4f5c\uff1aexpln \u5206\u6790 \u6839\u636e\u4f60\u7684\u95ee\u9898\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7 explain \u7684 extra \u5b57\u6bb5\u6765\u5224\u65ad\u67e5\u8be2\u662f\u5426\u5b58\u5728\u56de\u8868\u64cd\u4f5c\u3002 extra \u5b57\u6bb5\u89e3\u91ca\uff1a using index\uff1a\u4f7f\u7528\u7d22\u5f15\u8986\u76d6\uff0c\u67e5\u8be2\u5b57\u6bb5\u5168\u90e8\u5728\u7d22\u5f15\u4e2d\uff0c\u4e0d\u9700\u8981\u56de\u8868\u3002 using index condition\uff1a\u4f7f\u7528\u7d22\u5f15\u67e5\u627e\uff0c\u4f46\u9700\u8981\u6839\u636e\u8fc7\u6ee4\u6761\u4ef6\u5224\u65ad\uff0c\u4e5f\u4e0d\u9700\u8981\u56de\u8868\u3002 using index with where: \u4f7f\u7528\u7d22\u5f15\uff0c\u4f46\u9700\u8981\u6839\u636e where \u6761\u4ef6\u8fc7\u6ee4\uff0c\u9700\u8981\u56de\u8868\u3002 \u6848\u4f8b\u5206\u6790\uff1a \u4f60\u63d0\u4f9b\u7684 explain \u8f93\u51fa\u4e2d\uff0cextra \u4e3a\uff1a Using where; Using index; Using temporary; Using filesort \u767b\u5f55\u540e\u590d\u5236 \u7531\u4e8e extra \u4e2d\u5305\u542b &#8220;using where&#8221;\uff0c\u8fd9\u610f\u5473\u7740\u67e5\u8be2\u9700\u8981\u56de\u8868\u64cd\u4f5c\u3002 \u7ed3\u8bba\uff1a \u56e0\u6b64\uff0c\u6839\u636e explain \u5206\u6790\u7684\u7ed3\u679c\uff0c\u4f60\u7684\u67e5\u8be2\u8fd8\u5b58\u5728\u56de\u8868\u64cd\u4f5c\u3002 \u4ee5\u4e0a\u5c31\u662fExpln \u5206\u6790\u7ed3\u679c\u663e\u793a\u201cUsing where\u201d\uff0c\u8fd9\u662f\u5426\u610f\u5473\u7740\u67e5\u8be2\u5b58\u5728\u56de\u8868\u64cd\u4f5c\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},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-7962","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/7962","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=7962"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/7962\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=7962"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=7962"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=7962"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}