{"id":78420,"date":"2024-10-16T11:54:59","date_gmt":"2024-10-16T03:54:59","guid":{"rendered":"https:\/\/server.hk\/cnblog\/78420\/"},"modified":"2024-10-16T11:54:59","modified_gmt":"2024-10-16T03:54:59","slug":"mysql%e6%8c%87%e4%bb%a4-extra%ef%bc%88%e9%a1%8d%e5%a4%96%e4%bf%a1%e6%81%af%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/78420\/","title":{"rendered":"MySQL\u6307\u4ee4: EXTRA\uff08\u984d\u5916\u4fe1\u606f\uff09"},"content":{"rendered":"<h1 id=\"mysql%e6%8c%87%e4%bb%a4-extra%ef%bc%88%e9%a1%8d%e5%a4%96%e4%bf%a1%e6%81%af%ef%bc%89-IFlpVslcBL\">MySQL\u6307\u4ee4: EXTRA\uff08\u984d\u5916\u4fe1\u606f\uff09<\/h1>\n<p>\u5728\u4f7f\u7528MySQL\u9032\u884c\u6578\u64da\u5eab\u7ba1\u7406\u6642\uff0c\u4e86\u89e3\u5404\u7a2e\u6307\u4ee4\u53ca\u5176\u529f\u80fd\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002\u5176\u4e2d\uff0cEXTRA\uff08\u984d\u5916\u4fe1\u606f\uff09\u6307\u4ee4\u63d0\u4f9b\u4e86\u6709\u95dc\u67e5\u8a62\u57f7\u884c\u7684\u9644\u52a0\u4fe1\u606f\uff0c\u5e6b\u52a9\u7528\u6236\u66f4\u597d\u5730\u7406\u89e3\u67e5\u8a62\u7684\u6027\u80fd\u548c\u884c\u70ba\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eEXTRA\u6307\u4ee4\u7684\u7528\u9014\u3001\u5e38\u898b\u985e\u578b\u53ca\u5176\u5728\u6578\u64da\u5eab\u512a\u5316\u4e2d\u7684\u91cd\u8981\u6027\u3002<\/p>\n<h2 id=\"extra%e6%8c%87%e4%bb%a4%e7%9a%84%e6%a6%82%e8%bf%b0-IFlpVslcBL\">EXTRA\u6307\u4ee4\u7684\u6982\u8ff0<\/h2>\n<p>EXTRA\u6307\u4ee4\u662fMySQL\u5728\u57f7\u884c\u67e5\u8a62\u6642\u63d0\u4f9b\u7684\u9644\u52a0\u4fe1\u606f\uff0c\u901a\u5e38\u5728\u4f7f\u7528EXPLAIN\u8a9e\u53e5\u6642\u986f\u793a\u3002\u9019\u4e9b\u4fe1\u606f\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5eab\u7ba1\u7406\u54e1\u5206\u6790\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\uff0c\u5f9e\u800c\u9032\u884c\u5fc5\u8981\u7684\u512a\u5316\u3002EXTRA\u4fe1\u606f\u901a\u5e38\u5305\u62ec\u67e5\u8a62\u7684\u57f7\u884c\u65b9\u5f0f\u3001\u4f7f\u7528\u7684\u7d22\u5f15\u3001\u4ee5\u53ca\u662f\u5426\u5b58\u5728\u4efb\u4f55\u6f5b\u5728\u7684\u6027\u80fd\u554f\u984c\u3002<\/p>\n<h2 id=\"%e5%b8%b8%e8%a6%8b%e7%9a%84extra%e4%bf%a1%e6%81%af%e9%a1%9e%e5%9e%8b-IFlpVslcBL\">\u5e38\u898b\u7684EXTRA\u4fe1\u606f\u985e\u578b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684EXTRA\u4fe1\u606f\u985e\u578b\uff1a<\/p>\n<ul>\n<li><strong>Using index:<\/strong> \u8868\u793a\u67e5\u8a62\u4f7f\u7528\u4e86\u7d22\u5f15\uff0c\u9019\u901a\u5e38\u610f\u5473\u8457\u67e5\u8a62\u7684\u6027\u80fd\u8f03\u597d\u3002<\/li>\n<li><strong>Using where:<\/strong> \u8868\u793a\u67e5\u8a62\u4e2d\u4f7f\u7528\u4e86WHERE\u689d\u4ef6\u4f86\u904e\u6ffe\u7d50\u679c\uff0c\u9019\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u7684\u6027\u80fd\u3002<\/li>\n<li><strong>Using temporary:<\/strong> \u8868\u793a\u67e5\u8a62\u9700\u8981\u4f7f\u7528\u81e8\u6642\u8868\uff0c\u9019\u901a\u5e38\u6703\u5c0e\u81f4\u6027\u80fd\u4e0b\u964d\u3002<\/li>\n<li><strong>Using filesort:<\/strong> \u8868\u793a\u67e5\u8a62\u9700\u8981\u9032\u884c\u984d\u5916\u7684\u6392\u5e8f\u64cd\u4f5c\uff0c\u9019\u4e5f\u53ef\u80fd\u5f71\u97ff\u6027\u80fd\u3002<\/li>\n<li><strong>Distinct:<\/strong> \u8868\u793a\u67e5\u8a62\u4e2d\u4f7f\u7528\u4e86DISTINCT\u95dc\u9375\u5b57\uff0c\u9019\u53ef\u80fd\u6703\u589e\u52a0\u67e5\u8a62\u7684\u8907\u96dc\u6027\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8extra%e4%bf%a1%e6%81%af%e9%80%b2%e8%a1%8c%e6%9f%a5%e8%a9%a2%e5%84%aa%e5%8c%96-IFlpVslcBL\">\u5982\u4f55\u4f7f\u7528EXTRA\u4fe1\u606f\u9032\u884c\u67e5\u8a62\u512a\u5316<\/h2>\n<p>\u5229\u7528EXTRA\u4fe1\u606f\u9032\u884c\u67e5\u8a62\u512a\u5316\u7684\u904e\u7a0b\u901a\u5e38\u5305\u62ec\u4ee5\u4e0b\u5e7e\u500b\u6b65\u9a5f\uff1a<\/p>\n<ol>\n<li><strong>\u5206\u6790EXPLAIN\u8f38\u51fa\uff1a<\/strong> \u4f7f\u7528EXPLAIN\u8a9e\u53e5\u4f86\u67e5\u770b\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\uff0c\u4e26\u6ce8\u610fEXTRA\u5217\u4e2d\u7684\u4fe1\u606f\u3002<\/li>\n<li><strong>\u8b58\u5225\u6027\u80fd\u74f6\u9838\uff1a<\/strong> \u6839\u64daEXTRA\u4fe1\u606f\uff0c\u8b58\u5225\u53ef\u80fd\u5f71\u97ff\u67e5\u8a62\u6027\u80fd\u7684\u56e0\u7d20\uff0c\u4f8b\u5982\u4f7f\u7528\u81e8\u6642\u8868\u6216\u6587\u4ef6\u6392\u5e8f\u3002<\/li>\n<li><strong>\u8abf\u6574\u67e5\u8a62\u6216\u7d22\u5f15\uff1a<\/strong> \u6839\u64da\u5206\u6790\u7d50\u679c\uff0c\u8003\u616e\u8abf\u6574\u67e5\u8a62\u7d50\u69cb\u6216\u6dfb\u52a0\/\u4fee\u6539\u7d22\u5f15\uff0c\u4ee5\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002<\/li>\n<\/ol>\n<h3 id=\"%e7%a4%ba%e4%be%8b-IFlpVslcBL\">\u793a\u4f8b<\/h3>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528EXPLAIN\u8a9e\u53e5\u7684\u793a\u4f8b\uff1a<\/p>\n<pre><code>EXPLAIN SELECT * FROM users WHERE age &gt; 30;<\/code><\/pre>\n<p>\u57f7\u884c\u4e0a\u8ff0\u67e5\u8a62\u5f8c\uff0c\u60a8\u53ef\u80fd\u6703\u770b\u5230\u985e\u4f3c\u4ee5\u4e0b\u7684\u8f38\u51fa\uff1a<\/p>\n<pre><code>id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra\n---|--------------|-------|------|----------------|-----|---------|-----|------|----------------\n1  | SIMPLE       | users | ALL  | NULL           | NULL| NULL    | NULL| 1000 | Using where<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0cEXTRA\u986f\u793a\u201cUsing where\u201d\uff0c\u9019\u610f\u5473\u8457\u67e5\u8a62\u4f7f\u7528\u4e86WHERE\u689d\u4ef6\u4f86\u904e\u6ffe\u7d50\u679c\u3002\u9019\u53ef\u80fd\u8868\u660e\u9700\u8981\u9032\u4e00\u6b65\u512a\u5316\uff0c\u4f8b\u5982\u6dfb\u52a0\u7d22\u5f15\u4ee5\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-IFlpVslcBL\">\u7d50\u8ad6<\/h2>\n<p>EXTRA\u6307\u4ee4\u5728MySQL\u4e2d\u626e\u6f14\u8457\u91cd\u8981\u7684\u89d2\u8272\uff0c\u5e6b\u52a9\u7528\u6236\u7406\u89e3\u67e5\u8a62\u7684\u57f7\u884c\u904e\u7a0b\u53ca\u5176\u6027\u80fd\u3002\u901a\u904e\u5206\u6790EXTRA\u4fe1\u606f\uff0c\u958b\u767c\u8005\u548c\u6578\u64da\u5eab\u7ba1\u7406\u54e1\u53ef\u4ee5\u8b58\u5225\u6f5b\u5728\u7684\u6027\u80fd\u74f6\u9838\uff0c\u4e26\u9032\u884c\u76f8\u61c9\u7684\u512a\u5316\u3002\u9019\u4e0d\u50c5\u80fd\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\uff0c\u9084\u80fd\u6539\u5584\u6574\u9ad4\u6578\u64da\u5eab\u6027\u80fd\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u670d\u52d9\uff0c\u4ee5\u4fbf\u66f4\u597d\u5730\u7ba1\u7406\u60a8\u7684\u6578\u64da\u5eab\u548c\u61c9\u7528\u7a0b\u5e8f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u6307\u4ee4EXTRA\uff08\u984d\u5916\u4fe1\u606f\uff09\uff0c\u638c\u63e1\u5982\u4f55\u7372\u53d6\u67e5\u8a62\u7684\u9644\u52a0\u6578\u64da\uff0c\u63d0\u5347\u6578\u64da\u5eab\u64cd\u4f5c\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-78420","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78420","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=78420"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78420\/revisions"}],"predecessor-version":[{"id":78421,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78420\/revisions\/78421"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=78420"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=78420"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=78420"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}