{"id":10008093,"date":"2023-08-15T18:02:09","date_gmt":"2023-08-15T10:02:09","guid":{"rendered":"http:\/\/ityet.com\/?p=10008093"},"modified":"2023-08-15T18:02:09","modified_gmt":"2023-08-15T10:02:09","slug":"mysql-%e6%89%a7%e8%a1%8c%e8%ae%a1%e5%88%92%e8%af%a6%e8%a7%a3-%e4%ba%ac%e4%b8%9c%e7%89%a9%e6%b5%81%e6%8a%80%e6%9c%af%e5%9b%a2%e9%98%9f","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10008093","title":{"rendered":"MySQL \u6267\u884c\u8ba1\u5212\u8be6\u89e3 | \u4eac\u4e1c\u7269\u6d41\u6280\u672f\u56e2\u961f"},"content":{"rendered":"<h2>1. EXPLAIN\u8be6\u89e3<\/h2>\n<p>\u672c\u6587\u57fa\u4e8eMySQL 8.0\u7f16\u5199\uff0c\u7406\u8bba\u652f\u6301MySQL 5.0\u53ca\u66f4\u9ad8\u7248\u672c\u3002<\/p>\n<h2>2. EXPLAIN\u4f7f\u7528<\/h2>\n<h4>2.1 explain\u5206\u6790SQL\u7684\u6267\u884c\u8ba1\u5212<\/h4>\n<pre><code>{EXPLAIN | DESCRIBE | DESC}\n  tbl_name [col_name | wild]\n\n{EXPLAIN | DESCRIBE | DESC}\n    [explain_type]\n    {explainable_stmt | FOR CONNECTION connection_id}\n\n{EXPLAIN | DESCRIBE | DESC} ANALYZE select_statement    \n\nexplain_type: {\n    FORMAT = format_name\n}\n\nformat_name: {\n    TRADITIONAL\n  | JSON\n  | TREE\n}\n\nexplainable_stmt: {\n    SELECT statement\n  | TABLE statement\n  | DELETE statement\n  | INSERT statement\n  | REPLACE statement\n  | UPDATE statement\n}\n<\/code><\/pre>\n<h4>2.2 \u793a\u4f8b<\/h4>\n<pre><code>EXPLAIN format = TRADITIONAL json SELECT tt.TicketNumber, tt.TimeIn,\n        tt.ProjectReference, tt.EstimatedShipDate,\n        tt.ActualShipDate, tt.ClientID,\n        tt.ServiceCodes, tt.RepetitiveID,\n        tt.CurrentProcess, tt.CurrentDPPerson,\n        tt.RecordVolume, tt.DPPrinted, et.COUNTRY,\n        et_1.COUNTRY, do.CUSTNAME\nFROM tt, et, et AS et_1, do\nWHERE tt.SubmitTime IS NULL\n  AND tt.ActualPC = et.EMPLOYID\n  AND tt.AssignedPC = et_1.EMPLOYID\n  AND tt.ClientID = do.CUSTNMBR;\n<\/code><\/pre>\n<h4>2.3 \u7ed3\u679c\u8f93\u51fa\u5c55\u793a<\/h4>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044113747\" alt=\"\" title=\"\"><\/p>\n<h2>3. \u7ed3\u679c\u89e3\u8bfb<\/h2>\n<ul>\n<li><strong>id<\/strong>\uff1a\u8be5\u8bed\u53e5\u7684\u552f\u4e00\u6807\u8bc6\u3002\u5982\u679cexplain\u7684\u7ed3\u679c\u5305\u62ec\u591a\u4e2aid\u503c\uff0c\u5219\u6570\u5b57\u8d8a\u5927\u8d8a\u5148\u6267\u884c\uff1b\u800c\u5bf9\u4e8e\u76f8\u540cid\u7684\u884c\uff0c\u5219\u8868\u793a\u4ece\u4e0a\u5f80\u4e0b\u4f9d\u6b21\u6267\u884c\u3002<\/li>\n<li><strong>select_type<\/strong>\uff1a\u67e5\u8be2\u7c7b\u578b\uff0c\u6709\u5982\u4e0b\u51e0\u79cd\u53d6\u503c\uff1a<\/li>\n<\/ul>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044113748\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<ul>\n<li><strong>table<\/strong>\uff1a\u8868\u793a\u5f53\u524d\u8fd9\u4e00\u884c\u6b63\u5728\u8bbf\u95ee\u54ea\u5f20\u8868\uff0c\u5982\u679cSQL\u5b9a\u4e49\u4e86\u522b\u540d\uff0c\u5219\u5c55\u793a\u8868\u7684\u522b\u540d<\/li>\n<li><strong>partitions<\/strong>\uff1a\u5f53\u524d\u67e5\u8be2\u5339\u914d\u8bb0\u5f55\u7684\u5206\u533a\u3002\u5bf9\u4e8e\u672a\u5206\u533a\u7684\u8868\uff0c\u8fd4\u56denull<\/li>\n<li><strong>type<\/strong>\uff1a\u8fde\u63a5\u7c7b\u578b\uff0c\u6709\u5982\u4e0b\u51e0\u79cd\u53d6\u503c\uff0c\u6027\u80fd\u4ece\u597d\u5230\u574f\u6392\u5e8f\u5982\u4e0b\uff1a<\/li>\n<\/ul>\n<p>\u25e6<strong>system<\/strong>\uff1a\u8be5\u8868\u53ea\u6709\u4e00\u884c\uff08\u76f8\u5f53\u4e8e\u7cfb\u7edf\u8868\uff09\uff0csystem\u662fconst\u7c7b\u578b\u7684\u7279\u4f8b<\/p>\n<p>\u25e6<strong>const<\/strong>\uff1a\u9488\u5bf9\u4e3b\u952e\u6216\u552f\u4e00\u7d22\u5f15\u7684\u7b49\u503c\u67e5\u8be2\u626b\u63cf, \u6700\u591a\u53ea\u8fd4\u56de\u4e00\u884c\u6570\u636e. const \u67e5\u8be2\u901f\u5ea6\u975e\u5e38\u5feb, \u56e0\u4e3a\u5b83\u4ec5\u4ec5\u8bfb\u53d6\u4e00\u6b21\u5373\u53ef<\/p>\n<p>\u25e6<strong>eq_ref<\/strong>\uff1a\u5f53\u4f7f\u7528\u4e86\u7d22\u5f15\u7684\u5168\u90e8\u7ec4\u6210\u90e8\u5206\uff0c\u5e76\u4e14\u7d22\u5f15\u662fPRIMARY KEY\u6216UNIQUE NOT NULL \u624d\u4f1a\u4f7f\u7528\u8be5\u7c7b\u578b\uff0c\u6027\u80fd\u4ec5\u6b21\u4e8esystem\u53caconst\u3002<\/p>\n<pre><code>-- \u591a\u8868\u5173\u8054\u67e5\u8be2\uff0c\u5355\u884c\u5339\u914d\nSELECT * FROM ref_table,other_table\n  WHERE ref_table.key_column=other_table.column;\n\n-- \u591a\u8868\u5173\u8054\u67e5\u8be2\uff0c\u8054\u5408\u7d22\u5f15\uff0c\u591a\u884c\u5339\u914d\nSELECT * FROM ref_table,other_table\n  WHERE ref_table.key_column_part1=other_table.column\n  AND ref_table.key_column_part2=1;\n<\/code><\/pre>\n<p>\u25e6<strong>ref<\/strong>\uff1a\u5f53\u6ee1\u8db3\u7d22\u5f15\u7684\u6700\u5de6\u524d\u7f00\u89c4\u5219\uff0c\u6216\u8005\u7d22\u5f15\u4e0d\u662f\u4e3b\u952e\u4e5f\u4e0d\u662f\u552f\u4e00\u7d22\u5f15\u65f6\u624d\u4f1a\u53d1\u751f\u3002\u5982\u679c\u4f7f\u7528\u7684\u7d22\u5f15\u53ea\u4f1a\u5339\u914d\u5230\u5c11\u91cf\u7684\u884c\uff0c\u6027\u80fd\u4e5f\u662f\u4e0d\u9519\u7684\u3002<\/p>\n<pre><code>-- \u6839\u636e\u7d22\u5f15\uff08\u975e\u4e3b\u952e\uff0c\u975e\u552f\u4e00\u7d22\u5f15\uff09\uff0c\u5339\u914d\u5230\u591a\u884c\nSELECT * FROM ref_table WHERE key_column=expr;\n\n-- \u591a\u8868\u5173\u8054\u67e5\u8be2\uff0c\u5355\u4e2a\u7d22\u5f15\uff0c\u591a\u884c\u5339\u914d\nSELECT * FROM ref_table,other_table\n  WHERE ref_table.key_column=other_table.column;\n\n-- \u591a\u8868\u5173\u8054\u67e5\u8be2\uff0c\u8054\u5408\u7d22\u5f15\uff0c\u591a\u884c\u5339\u914d\nSELECT * FROM ref_table,other_table\n  WHERE ref_table.key_column_part1=other_table.column\n  AND ref_table.key_column_part2=1;\n<\/code><\/pre>\n<p><strong>TIPS\u6700\u5de6\u524d\u7f00\u539f\u5219<\/strong><\/p>\n<blockquote><p>\u6307\u7684\u662f\u7d22\u5f15\u6309\u7167\u6700\u5de6\u4f18\u5148\u7684\u65b9\u5f0f\u5339\u914d\u7d22\u5f15\u3002\u6bd4\u5982\u521b\u5efa\u4e86\u4e00\u4e2a\u7ec4\u5408\u7d22\u5f15(column1, column2, column3)\uff0c\u90a3\u4e48\uff0c\u5982\u679c\u67e5\u8be2\u6761\u4ef6\u662f\uff1a WHERE column1 = 1\u3001WHERE column1= 1 AND column2 = 2\u3001WHERE column1= 1 AND column2 = 2 AND column3 = 3 \u90fd\u53ef\u4ee5\u4f7f\u7528\u8be5\u7d22\u5f15\uff1b WHERE column1 = 2\u3001WHERE column1 = 1 AND column3 = 3\u5c31\u65e0\u6cd5\u5339\u914d\u8be5\u7d22\u5f15\u3002<\/p><\/blockquote>\n<p>\u25e6<strong>fulltext<\/strong>\uff1a\u5168\u6587\u7d22\u5f15ref\/_or\/_null\uff1a\u8be5\u7c7b\u578b\u7c7b\u4f3c\u4e8eref\uff0c\u4f46\u662fMySQL\u4f1a\u989d\u5916\u641c\u7d22\u54ea\u4e9b\u884c\u5305\u542b\u4e86NULL\u3002\u8fd9\u79cd\u7c7b\u578b\u5e38\u89c1\u4e8e\u89e3\u6790\u5b50\u67e5\u8be2<\/p>\n<pre><code>SELECT * FROM ref_table\nWHERE key_column=expr OR key_column IS NULL;\n<\/code><\/pre>\n<p>\u25e6<strong>index_merge<\/strong>\uff1a\u6b64\u7c7b\u578b\u8868\u793a\u4f7f\u7528\u4e86\u7d22\u5f15\u5408\u5e76\u4f18\u5316\uff0c\u8868\u793a\u4e00\u4e2a\u67e5\u8be2\u91cc\u9762\u7528\u5230\u4e86\u591a\u4e2a\u7d22\u5f15<\/p>\n<p>\u25e6<strong>unique_subquery<\/strong>\uff1a\u8be5\u7c7b\u578b\u548ceq\/_ref\u7c7b\u4f3c\uff0c\u4f46\u662f\u4f7f\u7528\u4e86IN\u67e5\u8be2\uff0c\u4e14\u5b50\u67e5\u8be2\u662f\u4e3b\u952e\u6216\u8005\u552f\u4e00\u7d22\u5f15\u3002\u4f8b\u5982\uff1avalue IN (SELECT primary\/_key FROM single\/_table WHERE some\/_expr)<\/p>\n<p>\u25e6<strong>index_subquery<\/strong>\uff1a\u548cunique\/_subquery\u7c7b\u4f3c\uff0c\u53ea\u662f\u5b50\u67e5\u8be2\u4f7f\u7528\u7684\u662f\u975e\u552f\u4e00\u7d22\u5f15\u3002value IN (SELECT key\/_column FROM single\/_table WHERE some\/_expr)<\/p>\n<p>\u25e6<strong>range<\/strong>\uff1a\u8303\u56f4\u626b\u63cf\uff0c\u8868\u793a\u68c0\u7d22\u4e86\u6307\u5b9a\u8303\u56f4\u7684\u884c\uff0c\u4e3b\u8981\u7528\u4e8e\u6709\u9650\u5236\u7684\u7d22\u5f15\u626b\u63cf\u3002\u6bd4\u8f83\u5e38\u89c1\u7684\u8303\u56f4\u626b\u63cf\u662f\u5e26\u6709BETWEEN\u5b50\u53e5\u6216WHERE\u5b50\u53e5\u91cc\u6709&gt;\u3001&gt;=\u3001&lt;\u3001&lt;=\u3001IS NULL\u3001&lt;=&gt;\u3001BETWEEN\u3001LIKE\u3001IN()\u7b49\u64cd\u4f5c\u7b26\u3002<\/p>\n<pre><code>SELECT * FROM tbl_name\n  WHERE key_column BETWEEN 10 and 20;\n\nSELECT * FROM tbl_name\n  WHERE key_column IN (10,20,30);\n<\/code><\/pre>\n<p>\u25e6<strong>index<\/strong>\uff1a\u5168\u7d22\u5f15\u626b\u63cf\uff0c\u548cALL\u7c7b\u4f3c\uff0c\u53ea\u4e0d\u8fc7index\u662f\u5168\u76d8\u626b\u63cf\u4e86\u7d22\u5f15\u7684\u6570\u636e\u3002\u5f53\u67e5\u8be2\u4ec5\u4f7f\u7528\u7d22\u5f15\u4e2d\u7684\u4e00\u90e8\u5206\u5217\u65f6\uff0c\u53ef\u4f7f\u7528\u6b64\u7c7b\u578b\u3002\u6709\u4e24\u79cd\u573a\u666f\u4f1a\u89e6\u53d1\uff1a<\/p>\n<p>\u25aa\u5982\u679c\u7d22\u5f15\u662f\u67e5\u8be2\u7684\u8986\u76d6\u7d22\u5f15\uff0c\u5e76\u4e14\u7d22\u5f15\u67e5\u8be2\u7684\u6570\u636e\u5c31\u53ef\u4ee5\u6ee1\u8db3\u67e5\u8be2\u4e2d\u6240\u9700\u7684\u6240\u6709\u6570\u636e\uff0c\u5219\u53ea\u626b\u63cf\u7d22\u5f15\u6811\u3002\u6b64\u65f6\uff0cexplain\u7684Extra \u5217\u7684\u7ed3\u679c\u662fUsing index\u3002index\u901a\u5e38\u6bd4ALL\u5feb\uff0c\u56e0\u4e3a\u7d22\u5f15\u7684\u5927\u5c0f\u901a\u5e38\u5c0f\u4e8e\u8868\u6570\u636e\u3002<\/p>\n<p>\u25aa\u6309\u7d22\u5f15\u7684\u987a\u5e8f\u6765\u67e5\u627e\u6570\u636e\u884c\uff0c\u6267\u884c\u4e86\u5168\u8868\u626b\u63cf\u3002\u6b64\u65f6\uff0cexplain\u7684Extra\u5217\u7684\u7ed3\u679c\u4e0d\u4f1a\u51fa\u73b0Uses index\u3002<\/p>\n<p>\u25e6<strong>ALL<\/strong>\uff1a\u5168\u8868\u626b\u63cf\uff0c\u6027\u80fd\u6700\u5dee\u3002<\/p>\n<ul>\n<li><strong>possible_keys<\/strong>\uff1a\u5c55\u793a\u5f53\u524d\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528\u54ea\u4e9b\u7d22\u5f15\uff0c\u8fd9\u4e00\u5217\u7684\u6570\u636e\u662f\u5728\u4f18\u5316\u8fc7\u7a0b\u7684\u65e9\u671f\u521b\u5efa\u7684\uff0c\u56e0\u6b64\u6709\u4e9b\u7d22\u5f15\u53ef\u80fd\u5bf9\u4e8e\u540e\u7eed\u4f18\u5316\u8fc7\u7a0b\u662f\u6ca1\u7528\u7684\u3002<\/li>\n<li><strong>key<\/strong>\uff1a\u8868\u793aMySQL\u5b9e\u9645\u9009\u62e9\u7684\u7d22\u5f15key\/_len\uff1a\u7d22\u5f15\u4f7f\u7528\u7684\u5b57\u8282\u6570\u3002\u7531\u4e8e\u5b58\u50a8\u683c\u5f0f\uff0c\u5f53\u5b57\u6bb5\u5141\u8bb8\u4e3aNULL\u65f6\uff0ckey\/_len\u6bd4\u4e0d\u5141\u8bb8\u4e3a\u7a7a\u65f6\u59271\u5b57\u8282\u3002<\/li>\n<\/ul>\n<p>\u25e6key_len\u8ba1\u7b97\u516c\u5f0f\uff1a<a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=%2Bwj%2BhYBy19sOyPbqqm9FIg%3D%3D.7iy4U%2BD%2Fowxp199ZQtvwnTiGppYgb%2F%2B2UmAYArEUq%2B6H%2FZlo7q%2BpylXNa2EiaKS1\" rel=\"noopener noreferrer\">https:\/\/www.cnblogs.com\/gomysql\/p\/4004244.html<\/a><\/p>\n<ul>\n<li><strong>ref<\/strong>\uff1a\u8868\u793a\u5c06\u54ea\u4e2a\u5b57\u6bb5\u6216\u5e38\u91cf\u548ckey\u5217\u6240\u4f7f\u7528\u7684\u5b57\u6bb5\u8fdb\u884c\u6bd4\u8f83\u3002\u5982\u679cref\u662f\u4e00\u4e2a\u51fd\u6570\uff0c\u5219\u4f7f\u7528\u7684\u503c\u662f\u51fd\u6570\u7684\u7ed3\u679c\u3002\u8981\u60f3\u67e5\u770b\u662f\u54ea\u4e2a\u51fd\u6570\uff0c\u53ef\u5728EXPLAIN\u8bed\u53e5\u4e4b\u540e\u7d27\u8ddf\u4e00\u4e2aSHOW WARNING\u8bed\u53e5\u3002<\/li>\n<li><strong>rows<\/strong>\uff1aMySQL\u4f30\u7b97\u4f1a\u626b\u63cf\u7684\u884c\u6570\uff0c\u6570\u503c\u8d8a\u5c0f\u8d8a\u597d\u3002<\/li>\n<li><strong>filtered<\/strong>\uff1a\u8868\u793a\u7b26\u5408\u67e5\u8be2\u6761\u4ef6\u7684\u6570\u636e\u767e\u5206\u6bd4\uff0c\u6700\u5927100\u3002\u7528rows \u00d7 filtered\u53ef\u83b7\u5f97\u548c\u4e0b\u4e00\u5f20\u8868\u8fde\u63a5\u7684\u884c\u6570\u3002\u4f8b\u5982rows = 1000\uff0cfiltered = 50%\uff0c\u5219\u548c\u4e0b\u4e00\u5f20\u8868\u8fde\u63a5\u7684\u884c\u6570\u662f500\u3002<\/li>\n<\/ul>\n<p><strong>TIPS<\/strong><\/p>\n<blockquote><p>\u5728MySQL 5.7\u4e4b\u524d\uff0c\u60f3\u8981\u663e\u793a\u6b64\u5b57\u6bb5\u9700\u4f7f\u7528explain extended\u547d\u4ee4\uff1b MySQL.5.7\u53ca\u66f4\u9ad8\u7248\u672c\uff0cexplain\u9ed8\u8ba4\u5c31\u4f1a\u5c55\u793afiltered<\/p><\/blockquote>\n<ul>\n<li><strong>Extra<\/strong>\uff1a\u5c55\u793a\u6709\u5173\u672c\u6b21\u67e5\u8be2\u7684\u9644\u52a0\u4fe1\u606f\uff0c\u53d6\u503c\u5982\u4e0b\uff1a<\/li>\n<\/ul>\n<p>\u25e6Child of \u2018table\u2019 pushed join@1\uff1a\u6b64\u503c\u53ea\u4f1a\u5728NDB Cluster\u4e0b\u51fa\u73b0\u3002<\/p>\n<p>\u25e6const row not found\uff1a\u4f8b\u5982\u67e5\u8be2\u8bed\u53e5SELECT \u2026 FROM tbl_name\uff0c\u800c\u8868\u662f\u7a7a\u7684<\/p>\n<p>\u25e6Deleting all rows\uff1a\u5bf9\u4e8eDELETE\u8bed\u53e5\uff0c\u67d0\u4e9b\u5f15\u64ce\uff08\u4f8b\u5982MyISAM\uff09\u652f\u6301\u4ee5\u4e00\u79cd\u7b80\u5355\u800c\u5feb\u901f\u7684\u65b9\u5f0f\u5220\u9664\u6240\u6709\u7684\u6570\u636e\uff0c\u5982\u679c\u4f7f\u7528\u4e86\u8fd9\u79cd\u4f18\u5316\uff0c\u5219\u663e\u793a\u6b64\u503c<\/p>\n<p>\u25e6Distinct\uff1a\u67e5\u627edistinct\u503c\uff0c\u5f53\u627e\u5230\u7b2c\u4e00\u4e2a\u5339\u914d\u7684\u884c\u540e\uff0c\u5c06\u505c\u6b62\u4e3a\u5f53\u524d\u884c\u7ec4\u5408\u641c\u7d22\u66f4\u591a\u884c<\/p>\n<p>\u25e6FirstMatch(tbl_name)\uff1a\u5f53\u524d\u4f7f\u7528\u4e86\u534a\u8fde\u63a5FirstMatch\u7b56\u7565\uff0c\u8be6\u89c1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=%2BHn3Uz7dgSZcRKjdbu3Qpg%3D%3D.9NvOBJFW5LGEyEBFAZt0aIDf1CePvX0LpKU7Ll1Rq0MmZbpmaCeZbhhW31MIlEGH\" rel=\"noopener noreferrer\">https:\/\/mariadb.com\/kb\/en\/firstmatch-strategy\/<\/a> \uff0c\u7ffb\u8bd1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=WMC0jZbOVNcJHwqvGev11w%3D%3D.8GyBaH6qljtKhKhUHZcnVRWVF8eL0b8EI1s71lICOxwoc%2BOQgCI37HJdqUURCqd6\" rel=\"noopener noreferrer\">https:\/\/www.cnblogs.com\/abclife\/p\/10895624.html<\/a><\/p>\n<p>\u25e6Full scan on NULL key\uff1a\u5b50\u67e5\u8be2\u4e2d\u7684\u4e00\u79cd\u4f18\u5316\u65b9\u5f0f\uff0c\u5728\u65e0\u6cd5\u901a\u8fc7\u7d22\u5f15\u8bbf\u95eenull\u503c\u7684\u65f6\u5019\u4f7f\u7528<\/p>\n<p>\u25e6Impossible HAVING\uff1aHAVING\u5b50\u53e5\u59cb\u7ec8\u4e3afalse\uff0c\u4e0d\u4f1a\u547d\u4e2d\u4efb\u4f55\u884c<\/p>\n<p>\u25e6Impossible WHERE\uff1aWHERE\u5b50\u53e5\u59cb\u7ec8\u4e3afalse\uff0c\u4e0d\u4f1a\u547d\u4e2d\u4efb\u4f55\u884c<\/p>\n<p>\u25e6Impossible WHERE noticed after reading const tables\uff1aMySQL\u5df2\u7ecf\u8bfb\u53d6\u4e86\u6240\u6709const\uff08\u6216system\uff09\u8868\uff0c\u5e76\u53d1\u73b0WHERE\u5b50\u53e5\u59cb\u7ec8\u4e3afalse<\/p>\n<p>\u25e6LooseScan(m\u2026n)\uff1a\u5f53\u524d\u4f7f\u7528\u4e86\u534a\u8fde\u63a5LooseScan\u7b56\u7565\uff0c\u8be6\u89c1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=LLikdQcF8hwbXKfcUkaZbQ%3D%3D.aB70XJBk7QDWH5aUi4RNI6VJxtoTyVPQSt8ylSm8BJ7eEFvZ2iGBbtR1PtImvplS\" rel=\"noopener noreferrer\">https:\/\/mariadb.com\/kb\/en\/loosescan-strategy\/<\/a> \uff0c\u7ffb\u8bd1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=8vMedj1bT8wwZOzSSbwgzA%3D%3D.ux1hQVpVcZ0UXqnB%2FCrwv0mw%2FMB%2BLQybRsmXcKymqAs%3D\" rel=\"noopener noreferrer\">http:\/\/www.javacoder.cn\/?p=39<\/a><\/p>\n<p>\u25e6No matching min\/max row\uff1a\u6ca1\u6709\u4efb\u4f55\u80fd\u6ee1\u8db3\u4f8b\u5982 SELECT MIN(\u2026) FROM \u2026 WHERE condition \u4e2d\u7684condition\u7684\u884c<\/p>\n<p>\u25e6no matching row in const table\uff1a\u5bf9\u4e8e\u5173\u8054\u67e5\u8be2\uff0c\u5b58\u5728\u4e00\u4e2a\u7a7a\u8868\uff0c\u6216\u8005\u6ca1\u6709\u884c\u80fd\u591f\u6ee1\u8db3\u552f\u4e00\u7d22\u5f15\u6761\u4ef6<\/p>\n<p>\u25e6No matching rows after partition pruning\uff1a\u5bf9\u4e8eDELETE\u6216UPDATE\u8bed\u53e5\uff0c\u4f18\u5316\u5668\u5728partition pruning\uff08\u5206\u533a\u4fee\u526a\uff09\u4e4b\u540e\uff0c\u627e\u4e0d\u5230\u8981delete\u6216update\u7684\u5185\u5bb9<\/p>\n<p>\u25e6No tables used\uff1a\u5f53\u6b64\u67e5\u8be2\u6ca1\u6709FROM\u5b50\u53e5\u6216\u62e5\u6709FROM DUAL\u5b50\u53e5\u65f6\u51fa\u73b0\u3002\u4f8b\u5982\uff1aexplain select 1<\/p>\n<p>\u25e6Not exists\uff1aMySQL\u80fd\u5bf9LEFT JOIN\u4f18\u5316\uff0c\u5728\u627e\u5230\u7b26\u5408LEFT JOIN\u7684\u884c\u540e\uff0c\u4e0d\u4f1a\u4e3a\u4e0a\u4e00\u884c\u7ec4\u5408\u4e2d\u68c0\u67e5\u6b64\u8868\u4e2d\u7684\u66f4\u591a\u884c\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT * FROM t1 LEFT JOIN t2 ON t1.id=t2.id\nWHERE t2.id IS NULL;\n<\/code><\/pre>\n<p>\u25e6\u5047\u8bbet2.id\u5b9a\u4e49\u6210\u4e86NOT NULL \uff0c\u6b64\u65f6\uff0cMySQL\u4f1a\u626b\u63cft1\uff0c\u5e76\u4f7f\u7528t1.id\u7684\u503c\u67e5\u627et2\u4e2d\u7684\u884c\u3002 \u5982\u679cMySQL\u5728t2\u4e2d\u627e\u5230\u4e00\u4e2a\u5339\u914d\u7684\u884c\uff0c\u5b83\u4f1a\u77e5\u9053t2.id\u6c38\u8fdc\u4e0d\u4f1a\u4e3aNULL\uff0c\u5e76\u4e14\u4e0d\u4f1a\u626b\u63cft2\u4e2d\u5177\u6709\u76f8\u540cid\u503c\u7684\u5176\u4f59\u884c\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5bf9\u4e8et1\u4e2d\u7684\u6bcf\u4e00\u884c\uff0cMySQL\u53ea\u9700\u8981\u5728t2\u4e2d\u53ea\u6267\u884c\u4e00\u6b21\u67e5\u627e\uff0c\u800c\u4e0d\u8003\u8651\u5728t2\u4e2d\u5b9e\u9645\u5339\u914d\u7684\u884c\u6570\u3002<\/p>\n<p>\u25e6\u5728MySQL 8.0.17\u53ca\u66f4\u9ad8\u7248\u672c\u4e2d\uff0c\u5982\u679c\u51fa\u73b0\u6b64\u63d0\u793a\uff0c\u8fd8\u53ef\u8868\u793a\u5f62\u5982 NOT IN (subquery) \u6216 NOT EXISTS (subquery) \u7684WHERE\u6761\u4ef6\u5df2\u7ecf\u5728\u5185\u90e8\u8f6c\u6362\u4e3a\u53cd\u8fde\u63a5\u3002\u8fd9\u5c06\u5220\u9664\u5b50\u67e5\u8be2\u5e76\u5c06\u5176\u8868\u653e\u5165\u6700\u9876\u5c42\u7684\u67e5\u8be2\u8ba1\u5212\u4e2d\uff0c\u4ece\u800c\u6539\u8fdb\u67e5\u8be2\u7684\u5f00\u9500\u3002\u901a\u8fc7\u5408\u5e76\u534a\u8fde\u63a5\u548c\u53cd\u8054\u63a5\uff0c\u4f18\u5316\u5668\u53ef\u4ee5\u66f4\u52a0\u81ea\u7531\u5730\u5bf9\u6267\u884c\u8ba1\u5212\u4e2d\u7684\u8868\u91cd\u65b0\u6392\u5e8f\uff0c\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c\u53ef\u8ba9\u67e5\u8be2\u63d0\u901f\u3002\u4f60\u53ef\u4ee5\u901a\u8fc7\u5728EXPLAIN\u8bed\u53e5\u540e\u7d27\u8ddf\u4e00\u4e2aSHOW WARNING\u8bed\u53e5\uff0c\u5e76\u5206\u6790\u7ed3\u679c\u4e2d\u7684Message\u5217\uff0c\u4ece\u800c\u67e5\u770b\u4f55\u65f6\u5bf9\u8be5\u67e5\u8be2\u6267\u884c\u4e86\u53cd\u8054\u63a5\u8f6c\u6362\u3002<\/p>\n<p>\u25e6Note\uff1a\u4e24\u8868\u5173\u8054\u53ea\u8fd4\u56de\u4e3b\u8868\u7684\u6570\u636e\uff0c\u5e76\u4e14\u53ea\u8fd4\u56de\u4e3b\u8868\u4e0e\u5b50\u8868\u6ca1\u5173\u8054\u4e0a\u7684\u6570\u636e\uff0c\u8fd9\u79cd\u8fde\u63a5\u5c31\u53eb\u53cd\u8fde\u63a5Plan isn\u2019t ready yet\uff1a\u4f7f\u7528\u4e86EXPLAIN FOR CONNECTION\uff0c\u5f53\u4f18\u5316\u5668\u5c1a\u672a\u5b8c\u6210\u4e3a\u5728\u6307\u5b9a\u8fde\u63a5\u4e2d\u4e3a\u6267\u884c\u7684\u8bed\u53e5\u521b\u5efa\u6267\u884c\u8ba1\u5212\u65f6\uff0c \u5c31\u4f1a\u51fa\u73b0\u6b64\u503c\u3002MySQL\u6ca1\u6709\u627e\u5230\u5408\u9002\u7684\u7d22\u5f15\u53bb\u4f7f\u7528\uff0c\u4f46\u662f\u53bb\u68c0\u67e5\u662f\u5426\u53ef\u4ee5\u4f7f\u7528range\u6216index_merge\u6765\u68c0\u7d22\u884c\u65f6\uff0c\u4f1a\u51fa\u73b0\u6b64\u63d0\u793a\u3002index map N\u7d22\u5f15\u7684\u7f16\u53f7\u4ece1\u5f00\u59cb\uff0c\u6309\u7167\u4e0e\u8868\u7684SHOW INDEX\u6240\u793a\u76f8\u540c\u7684\u987a\u5e8f\u3002 \u7d22\u5f15\u6620\u5c04\u503cN\u662f\u6307\u793a\u54ea\u4e9b\u7d22\u5f15\u662f\u5019\u9009\u7684\u4f4d\u63a9\u7801\u503c\u3002 \u4f8b\u59820x19\uff08\u4e8c\u8fdb\u523611001\uff09\u7684\u503c\u610f\u5473\u7740\u5c06\u8003\u8651\u7d22\u5f151\u30014\u548c5\u3002<\/p>\n<ul>\n<li>Plan isn\u2019t ready yet\uff1a\u4f7f\u7528\u4e86EXPLAIN FOR CONNECTION\uff0c\u5f53\u4f18\u5316\u5668\u5c1a\u672a\u5b8c\u6210\u4e3a\u5728\u6307\u5b9a\u8fde\u63a5\u4e2d\u4e3a\u6267\u884c\u7684\u8bed\u53e5\u521b\u5efa\u6267\u884c\u8ba1\u5212\u65f6\uff0c \u5c31\u4f1a\u51fa\u73b0\u6b64\u503c\u3002<\/li>\n<\/ul>\n<p>\u25e6MySQL\u6ca1\u6709\u627e\u5230\u5408\u9002\u7684\u7d22\u5f15\u53bb\u4f7f\u7528\uff0c\u4f46\u662f\u53bb\u68c0\u67e5\u662f\u5426\u53ef\u4ee5\u4f7f\u7528range\u6216index_merge\u6765\u68c0\u7d22\u884c\u65f6\uff0c\u4f1a\u51fa\u73b0\u6b64\u63d0\u793a\u3002index map N\u7d22\u5f15\u7684\u7f16\u53f7\u4ece1\u5f00\u59cb\uff0c\u6309\u7167\u4e0e\u8868\u7684SHOW INDEX\u6240\u793a\u76f8\u540c\u7684\u987a\u5e8f\u3002 \u7d22\u5f15\u6620\u5c04\u503cN\u662f\u6307\u793a\u54ea\u4e9b\u7d22\u5f15\u662f\u5019\u9009\u7684\u4f4d\u63a9\u7801\u503c\u3002 \u4f8b\u59820x19\uff08\u4e8c\u8fdb\u523611001\uff09\u7684\u503c\u610f\u5473\u7740\u5c06\u8003\u8651\u7d22\u5f151\u30014\u548c5\u3002<\/p>\n<p>\u25e6\u793a\u4f8b\uff1a\u4e0b\u9762\u4f8b\u5b50\u4e2d\uff0cname\u662fvarchar\u7c7b\u578b\uff0c\u4f46\u662f\u6761\u4ef6\u7ed9\u51fa\u6574\u6570\u578b\uff0c\u6d89\u53ca\u5230\u9690\u5f0f\u8f6c\u6362\u3002\u56fe\u4e2dt2\u4e5f\u6ca1\u6709\u7528\u5230\u7d22\u5f15\uff0c\u662f\u56e0\u4e3a\u67e5\u8be2\u4e4b\u524d\u6211\u5c06t2\u4e2dname\u5b57\u6bb5\u6392\u5e8f\u89c4\u5219\u6539\u4e3autf8_bin\u5bfc\u81f4\u7684\u94fe\u63a5\u5b57\u6bb5\u6392\u5e8f\u89c4\u5219\u4e0d\u5339\u914d\u3002<\/p>\n<pre><code>explain select a.* from t1 a left  join t2 b\non t1.name = t2.name\nwhere t2.name = 2;\n<\/code><\/pre>\n<ul>\n<li>\u7ed3\u679c\uff1a<\/li>\n<\/ul>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044113749\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<ul>\n<li>Recursive\uff1a\u51fa\u73b0\u4e86\u9012\u5f52\u67e5\u8be2\u3002\u8be6\u89c1\u201cWITH (Common Table Expressions)\u201d<\/li>\n<li>Rematerialize\uff1a\u7528\u5f97\u5f88\u5c11\uff0c\u4f7f\u7528\u7c7b\u4f3c\u5982\u4e0bSQL\u65f6\uff0c\u4f1a\u5c55\u793aRematerialize<\/li>\n<\/ul>\n<pre><code>SELECT\n  ...\nFROM\n  t,\n  LATERAL (derived table that refers to t) AS dt\n...\n<\/code><\/pre>\n<ul>\n<li>Scanned N databases\uff1a\u8868\u793a\u5728\u5904\u7406INFORMATION\/_SCHEMA\u8868\u7684\u67e5\u8be2\u65f6\uff0c\u626b\u63cf\u4e86\u51e0\u4e2a\u76ee\u5f55\uff0cN\u7684\u53d6\u503c\u53ef\u4ee5\u662f0\uff0c1\u6216\u8005all\u3002\u8be6\u89c1 \u201cOptimizing INFORMATION\/_SCHEMA Queries\u201d<\/li>\n<li>Select tables optimized away\uff1a\u4f18\u5316\u5668\u786e\u5b9a\uff1a\u2460\u6700\u591a\u8fd4\u56de1\u884c\uff1b\u2461\u8981\u4ea7\u751f\u8be5\u884c\u7684\u6570\u636e\uff0c\u8981\u8bfb\u53d6\u4e00\u7ec4\u786e\u5b9a\u7684\u884c\uff0c\u65f6\u4f1a\u51fa\u73b0\u6b64\u63d0\u793a\u3002\u4e00\u822c\u5728\u7528\u67d0\u4e9b\u805a\u5408\u51fd\u6570\u8bbf\u95ee\u5b58\u5728\u7d22\u5f15\u7684\u67d0\u4e2a\u5b57\u6bb5\u65f6\uff0c\u4f18\u5316\u5668\u4f1a\u901a\u8fc7\u7d22\u5f15\u76f4\u63a5\u4e00\u6b21\u5b9a\u4f4d\u5230\u6240\u9700\u8981\u7684\u6570\u636e\u884c\u5b8c\u6210\u6574\u4e2a\u67e5\u8be2\u65f6\u5c55\u793a\uff0c\u4f8b\u5982\u4e0b\u9762\u8fd9\u6761SQL\u3002<\/li>\n<\/ul>\n<pre><code>explain\nselect min(id)\nfrom t1;\n<\/code><\/pre>\n<ul>\n<li>Skip\/_open\/_table\uff0c Open\/_frm\/_only\uff0c Open\/_full\/_table\uff1a\u8fd9\u4e9b\u503c\u8868\u793a\u9002\u7528\u4e8eINFORMATION_SCHEMA\u8868\u67e5\u8be2\u7684\u6587\u4ef6\u6253\u5f00\u4f18\u5316\uff1b<\/li>\n<\/ul>\n<p>\u25e6Skip\/_open\/_table\uff1a\u65e0\u9700\u6253\u5f00\u8868\u6587\u4ef6\uff0c\u4fe1\u606f\u5df2\u7ecf\u901a\u8fc7\u626b\u63cf\u6570\u636e\u5b57\u5178\u83b7\u5f97<\/p>\n<p>\u25e6Open\/_frm\/_only\uff1a\u4ec5\u9700\u8981\u8bfb\u53d6\u6570\u636e\u5b57\u5178\u4ee5\u83b7\u53d6\u8868\u4fe1\u606f<\/p>\n<p>\u25e6Open\/_full\/_table\uff1a\u672a\u4f18\u5316\u7684\u4fe1\u606f\u67e5\u627e\u3002\u8868\u4fe1\u606f\u5fc5\u987b\u4ece\u6570\u636e\u5b57\u5178\u4ee5\u53ca\u8868\u6587\u4ef6\u4e2d\u8bfb\u53d6Start temporary, End temporary\uff1a\u8868\u793a\u4e34\u65f6\u8868\u4f7f\u7528Duplicate Weedout\u7b56\u7565\uff0c\u8be6\u89c1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=PmgSiiiqQPwHg5Tmky6DDA%3D%3D.03xub%2FwXXd8e0skI0fxyDfs%2B0SJlDguDi1p3I8o%2Ba7dkqvNo0%2BlRa40ZIVrg7PuliwU4Sl171%2FSchS7rtLKV8A%3D%3D\" rel=\"noopener noreferrer\">https:\/\/mariadb.com\/kb\/en\/duplicateweedout-strategy\/<\/a> \uff0c\u7ffb\u8bd1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=BSu1KGi5qbmGrB4aQc0ytA%3D%3D.bVCv7psUoBoNJRcBmyAzUApsrGCndwFqqf5tR10sKioBfLznzcLW06yEriJ3TMT0\" rel=\"noopener noreferrer\">https:\/\/www.cnblogs.com\/abclife\/p\/10895531.html<\/a><\/p>\n<ul>\n<li>unique row not found\uff1a\u5bf9\u4e8e\u5f62\u5982 SELECT \u2026 FROM tbl_name \u7684\u67e5\u8be2\uff0c\u4f46\u6ca1\u6709\u884c\u80fd\u591f\u6ee1\u8db3\u552f\u4e00\u7d22\u5f15\u6216\u4e3b\u952e\u67e5\u8be2\u7684\u6761\u4ef6<\/li>\n<li>Using filesort\uff1a\u5f53Query \u4e2d\u5305\u542b ORDER BY \u64cd\u4f5c\uff0c\u800c\u4e14\u65e0\u6cd5\u5229\u7528\u7d22\u5f15\u5b8c\u6210\u6392\u5e8f\u64cd\u4f5c\u7684\u65f6\u5019\uff0cMySQL Query Optimizer \u4e0d\u5f97\u4e0d\u9009\u62e9\u76f8\u5e94\u7684\u6392\u5e8f\u7b97\u6cd5\u6765\u5b9e\u73b0\u3002\u6570\u636e\u8f83\u5c11\u65f6\u4ece\u5185\u5b58\u6392\u5e8f\uff0c\u5426\u5219\u4ece\u78c1\u76d8\u6392\u5e8f\u3002Explain\u4e0d\u4f1a\u663e\u793a\u7684\u544a\u8bc9\u5ba2\u6237\u7aef\u7528\u54ea\u79cd\u6392\u5e8f\u3002\u5b98\u65b9\u89e3\u91ca\uff1a\u201cMySQL\u9700\u8981\u989d\u5916\u7684\u4e00\u6b21\u4f20\u9012\uff0c\u4ee5\u627e\u51fa\u5982\u4f55\u6309\u6392\u5e8f\u987a\u5e8f\u68c0\u7d22\u884c\u3002\u901a\u8fc7\u6839\u636e\u8054\u63a5\u7c7b\u578b\u6d4f\u89c8\u6240\u6709\u884c\u5e76\u4e3a\u6240\u6709\u5339\u914dWHERE\u5b50\u53e5\u7684\u884c\u4fdd\u5b58\u6392\u5e8f\u5173\u952e\u5b57\u548c\u884c\u7684\u6307\u9488\u6765\u5b8c\u6210\u6392\u5e8f\u3002\u7136\u540e\u5173\u952e\u5b57\u88ab\u6392\u5e8f\uff0c\u5e76\u6309\u6392\u5e8f\u987a\u5e8f\u68c0\u7d22\u884c\u201dUsing index\uff1a\u4ec5\u4f7f\u7528\u7d22\u5f15\u6811\u4e2d\u7684\u4fe1\u606f\u4ece\u8868\u4e2d\u68c0\u7d22\u5217\u4fe1\u606f\uff0c\u800c\u4e0d\u5fc5\u8fdb\u884c\u5176\u4ed6\u67e5\u627e\u4ee5\u8bfb\u53d6\u5b9e\u9645\u884c\u3002\u5f53\u67e5\u8be2\u4ec5\u4f7f\u7528\u5c5e\u4e8e\u5355\u4e2a\u7d22\u5f15\u7684\u5217\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528\u6b64\u7b56\u7565\u3002\u4f8b\u5982\uff1aexplain SELECT id FROM t<\/li>\n<li>Using index condition\uff1a\u8868\u793a\u5148\u6309\u6761\u4ef6\u8fc7\u6ee4\u7d22\u5f15\uff0c\u8fc7\u6ee4\u5b8c\u7d22\u5f15\u540e\u627e\u5230\u6240\u6709\u7b26\u5408\u7d22\u5f15\u6761\u4ef6\u7684\u6570\u636e\u884c\uff0c\u968f\u540e\u7528 WHERE \u5b50\u53e5\u4e2d\u7684\u5176\u4ed6\u6761\u4ef6\u53bb\u8fc7\u6ee4\u8fd9\u4e9b\u6570\u636e\u884c\u3002\u901a\u8fc7\u8fd9\u79cd\u65b9\u5f0f\uff0c\u9664\u975e\u6709\u5fc5\u8981\uff0c\u5426\u5219\u7d22\u5f15\u4fe1\u606f\u5c06\u53ef\u4ee5\u5ef6\u8fdf\u201c\u4e0b\u63a8\u201d\u8bfb\u53d6\u6574\u4e2a\u884c\u7684\u6570\u636e\u3002\u8be6\u89c1 \u201cIndex Condition Pushdown Optimization\u201d \u3002\u4f8b\u5982\uff1a<\/li>\n<li>MySQL\u5206\u6210\u4e86Server\u5c42\u548c\u5f15\u64ce\u5c42\uff0c\u4e0b\u63a8\u6307\u7684\u662f\u5c06\u8bf7\u6c42\u4ea4\u7ed9\u5f15\u64ce\u5c42\u5904\u7406\u3002\u7406\u89e3\u8fd9\u4e2a\u529f\u80fd\uff0c\u53ef\u521b\u5efa\u6240\u4ee5INDEX (zipcode, lastname, firstname)\uff0c\u5e76\u5206\u522b\u7528\u5982\u4e0b\u6307\u4ee4\uff0c<\/li>\n<\/ul>\n<pre><code>SET optimizer_switch = 'index_condition_pushdown=off'; \nSET optimizer_switch = 'index_condition_pushdown=on';\n<\/code><\/pre>\n<ul>\n<li>\u5f00\u6216\u8005\u5173\u95ed\u7d22\u5f15\u6761\u4ef6\u4e0b\u63a8\uff0c\u5e76\u5bf9\u6bd4\uff1a<\/li>\n<\/ul>\n<pre><code>explain SELECT * FROM people\nWHERE zipcode='95054'\nAND lastname LIKE '%etrunia%'\nAND address LIKE '%Main Street%';\n<\/code><\/pre>\n<ul>\n<li>\u7684\u6267\u884c\u7ed3\u679c\u3002index condition pushdown\u4eceMySQL 5.6\u5f00\u59cb\u652f\u6301\uff0c\u662fMySQL\u9488\u5bf9\u7279\u5b9a\u573a\u666f\u7684\u4f18\u5316\u673a\u5236\uff0c\u611f\u5174\u8da3\u7684\u53ef\u4ee5\u770b\u4e0b <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=l4P%2F1xQyP61Uo9TDsICuQA%3D%3D.lZJL82PrSdZ0q0rgSBEpYSngXtoJ%2FSU552QSJd1PQTG2ChqzdhXRDHv8thGs8YMR\" rel=\"noopener noreferrer\">https:\/\/blog.51cto.com\/lee90\/2060449<\/a><\/li>\n<li>Using index for group-by\uff1a\u6570\u636e\u8bbf\u95ee\u548c Using index \u4e00\u6837\uff0c\u6240\u9700\u6570\u636e\u53ea\u987b\u8981\u8bfb\u53d6\u7d22\u5f15\uff0c\u5f53Query \u4e2d\u4f7f\u7528GROUP BY\u6216DISTINCT \u5b50\u53e5\u65f6\uff0c\u5982\u679c\u5206\u7ec4\u5b57\u6bb5\u4e5f\u5728\u7d22\u5f15\u4e2d\uff0cExtra\u4e2d\u7684\u4fe1\u606f\u5c31\u4f1a\u662f Using index for group-by\u3002\u8be6\u89c1 \u201cGROUP BY Optimization\u201d<\/li>\n<\/ul>\n<pre><code>-- name\u5b57\u6bb5\u6709\u7d22\u5f15\nexplain SELECT name FROM t1 group by name\n<\/code><\/pre>\n<ul>\n<li>Using index for skip scan\uff1a\u8868\u793a\u4f7f\u7528\u4e86Skip Scan\u3002\u8be6\u89c1 Skip Scan Range Access Method<\/li>\n<li>Using join buffer (Block Nested Loop), Using join buffer (Batched Key Access)\uff1a\u4f7f\u7528Block Nested Loop\u6216Batched Key Access\u7b97\u6cd5\u63d0\u9ad8join\u7684\u6027\u80fd\u3002\u8be6\u89c1 <a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=715kfEoS%2BSQbTjkQCJccgA%3D%3D.iFU2MoutfV4vKVQV8rLk03JSm5FRf2elbMJy2uh8gPjZ%2Bi2wuUL93mLKEem3tO63uceEY5aB61Obzeh1RQ6c9A%3D%3D\" rel=\"noopener noreferrer\">https:\/\/www.cnblogs.com\/chenpingzhao\/p\/6720531.html<\/a><\/li>\n<li>Using MRR\uff1a\u4f7f\u7528\u4e86Multi-Range Read\u4f18\u5316\u7b56\u7565\u3002\u8be6\u89c1 \u201cMulti-Range Read Optimization\u201dUsing sort\/_union(\u2026), Using union(\u2026), Using intersect(\u2026)\uff1a\u8fd9\u4e9b\u6307\u793a\u7d22\u5f15\u626b\u63cf\u5982\u4f55\u5408\u5e76\u4e3aindex\/_merge\u8fde\u63a5\u7c7b\u578b\u3002\u8be6\u89c1 \u201cIndex Merge Optimization\u201d<\/li>\n<li>Using temporary\uff1a\u4e3a\u4e86\u89e3\u51b3\u8be5\u67e5\u8be2\uff0cMySQL\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u4e34\u65f6\u8868\u6765\u4fdd\u5b58\u7ed3\u679c\u3002\u5982\u679c\u67e5\u8be2\u5305\u542b\u4e0d\u540c\u5217\u7684GROUP BY\u548c ORDER BY\u5b50\u53e5\uff0c\u901a\u5e38\u4f1a\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u3002<\/li>\n<\/ul>\n<pre><code>-- name\u65e0\u7d22\u5f15\nexplain SELECT name FROM t1 group by name\n<\/code><\/pre>\n<ul>\n<li>Using where\uff1a\u5982\u679c\u6211\u4eec\u4e0d\u662f\u8bfb\u53d6\u8868\u7684\u6240\u6709\u6570\u636e\uff0c\u6216\u8005\u4e0d\u662f\u4ec5\u4ec5\u901a\u8fc7\u7d22\u5f15\u5c31\u53ef\u4ee5\u83b7\u53d6\u6240\u6709\u9700\u8981\u7684\u6570\u636e\uff0c\u5219\u4f1a\u51fa\u73b0using where\u4fe1\u606f<\/li>\n<\/ul>\n<pre><code>explain SELECT * FROM t1 where id &gt; 5\n<\/code><\/pre>\n<ul>\n<li>Using where with pushed condition\uff1a\u4ec5\u7528\u4e8eNDB<\/li>\n<li>Zero limit\uff1a\u8be5\u67e5\u8be2\u6709\u4e00\u4e2alimit 0\u5b50\u53e5\uff0c\u4e0d\u80fd\u9009\u62e9\u4efb\u4f55\u884cexplain SELECT name FROM resource_template limit 0<\/li>\n<\/ul>\n<h2>4. \u6269\u5c55\u7684EXPLAIN<\/h2>\n<ul>\n<li>EXPLAIN\u53ef\u4ea7\u751f\u989d\u5916\u7684\u6269\u5c55\u4fe1\u606f\uff0c\u53ef\u901a\u8fc7\u5728EXPLAIN\u8bed\u53e5\u540e\u7d27\u8ddf\u4e00\u6761SHOW WARNING\u8bed\u53e5\u67e5\u770b\u6269\u5c55\u4fe1\u606f\u3002<\/li>\n<li><strong>TIPS<\/strong><\/li>\n<\/ul>\n<blockquote><p>\u5728MySQL 8.0.12\u53ca\u66f4\u9ad8\u7248\u672c\uff0c\u6269\u5c55\u4fe1\u606f\u53ef\u7528\u4e8eSELECT\u3001DELETE\u3001INSERT\u3001REPLACE\u3001UPDATE\u8bed\u53e5\uff1b\u5728MySQL 8.0.12\u4e4b\u524d\uff0c\u6269\u5c55\u4fe1\u606f\u4ec5\u9002\u7528\u4e8eSELECT\u8bed\u53e5\uff1b \u5728MySQL 5.6\u53ca\u66f4\u4f4e\u7248\u672c\uff0c\u9700\u4f7f\u7528EXPLAIN EXTENDED xxx\u8bed\u53e5\uff1b\u800c\u4eceMySQL 5.7\u5f00\u59cb\uff0c\u65e0\u9700\u6dfb\u52a0EXTENDED\u5173\u952e\u8bcd\u3002<\/p><\/blockquote>\n<ul>\n<li>\u4f7f\u7528\u793a\u4f8b\uff1a<\/li>\n<\/ul>\n<pre><code>mysql&gt; EXPLAIN\n   SELECT t1.a, t1.a IN (SELECT t2.a FROM t2) FROM t1\/G\n*************************** 1. row ***************************\n          id: 1\n  select_type: PRIMARY\n        table: t1\n        type: index\npossible_keys: NULL\n          key: PRIMARY\n      key_len: 4\n          ref: NULL\n        rows: 4\n    filtered: 100.00\n        Extra: Using index\n*************************** 2. row ***************************\n          id: 2\n  select_type: SUBQUERY\n        table: t2\n        type: index\npossible_keys: a\n          key: a\n      key_len: 5\n          ref: NULL\n        rows: 3\n    filtered: 100.00\n        Extra: Using index\n2 rows in set, 1 warning (0.00 sec)\n\nmysql&gt; SHOW WARNINGS\/G\n*************************** 1. row ***************************\n  Level: Note\n  Code: 1003\nMessage: \/* select#1 *\/ select `test`.`t1`.`a` AS `a`,\n        &lt;in_optimizer&gt;(`test`.`t1`.`a`,`test`.`t1`.`a` in\n        ( &lt;materialize&gt; (\/* select#2 *\/ select `test`.`t2`.`a`\n        from `test`.`t2` where 1 having 1 ),\n        &lt;primary_index_lookup&gt;(`test`.`t1`.`a` in\n        &lt;temporary table&gt; on &lt;auto_key&gt;\n        where ((`test`.`t1`.`a` = `materialized-subquery`.`a`))))) AS `t1.a\n        IN (SELECT t2.a FROM t2)` from `test`.`t1`\n1 row in set (0.00 sec)\n<\/code><\/pre>\n<ul>\n<li>\u7531\u4e8eSHOW WARNING\u7684\u7ed3\u679c\u5e76\u4e0d\u4e00\u5b9a\u662f\u4e00\u4e2a\u6709\u6548SQL\uff0c\u4e5f\u4e0d\u4e00\u5b9a\u80fd\u591f\u6267\u884c\uff08\u56e0\u4e3a\u91cc\u9762\u5305\u542b\u4e86\u5f88\u591a\u7279\u6b8a\u6807\u8bb0\uff09\u3002\u7279\u6b8a\u6807\u8bb0\u53d6\u503c\u5982\u4e0b\uff1a<\/li>\n<\/ul>\n<p>\u25e6&lt;auto_key&gt;\uff1a\u81ea\u52a8\u751f\u6210\u7684\u4e34\u65f6\u8868key<\/p>\n<p>\u25e6&lt;cache&gt;(expr)\uff1a\u8868\u8fbe\u5f0f\uff08\u4f8b\u5982\u6807\u91cf\u5b50\u67e5\u8be2\uff09\u6267\u884c\u4e86\u4e00\u6b21\uff0c\u5e76\u4e14\u5c06\u503c\u4fdd\u5b58\u5728\u4e86\u5185\u5b58\u4e2d\u4ee5\u5907\u4ee5\u540e\u4f7f\u7528\u3002\u5bf9\u4e8e\u5305\u62ec\u591a\u4e2a\u503c\u7684\u7ed3\u679c\uff0c\u53ef\u80fd\u4f1a\u521b\u5efa\u4e34\u65f6\u8868\uff0c\u4f60\u5c06\u4f1a\u770b\u5230 &lt;temporary table&gt; \u7684\u5b57\u6837<\/p>\n<p>\u25e6&lt;exists&gt;(query fragment)\uff1a\u5b50\u67e5\u8be2\u88ab\u8f6c\u6362\u4e3a EXISTS<\/p>\n<p>\u25e6&lt;in_optimizer&gt;(query fragment)\uff1a\u8fd9\u662f\u4e00\u4e2a\u5185\u90e8\u4f18\u5316\u5668\u5bf9\u8c61\uff0c\u5bf9\u7528\u6237\u6ca1\u6709\u4efb\u4f55\u610f\u4e49<\/p>\n<p>\u25e6&lt;index_lookup&gt;(query fragment)\uff1a\u4f7f\u7528\u7d22\u5f15\u67e5\u627e\u6765\u5904\u7406\u67e5\u8be2\u7247\u6bb5\uff0c\u4ece\u800c\u627e\u5230\u5408\u683c\u7684\u884c<\/p>\n<p>\u25e6&lt;if&gt;(condition, expr1, expr2)\uff1a\u5982\u679c\u6761\u4ef6\u662ftrue\uff0c\u5219\u53d6expr1\uff0c\u5426\u5219\u53d6expr2<\/p>\n<p>\u25e6&lt;is\/_not\/_null_test&gt;(expr)\uff1a\u9a8c\u8bc1\u8868\u8fbe\u5f0f\u4e0d\u4e3aNULL\u7684\u6d4b\u8bd5<\/p>\n<p>\u25e6&lt;materialize&gt;(query fragment)\uff1a\u4f7f\u7528\u5b50\u67e5\u8be2\u5b9e\u73b0<\/p>\n<p>\u25e6materialized-subquery.col\/_name\uff1a\u5728\u5185\u90e8\u7269\u5316\u4e34\u65f6\u8868\u4e2d\u5bf9col\/_name\u7684\u5f15\u7528\uff0c\u4ee5\u4fdd\u5b58\u5b50\u67e5\u8be2\u7684\u7ed3\u679c<\/p>\n<p>\u25e6&lt;primary\/_index\/_lookup&gt;(query fragment)\uff1a\u4f7f\u7528\u4e3b\u952e\u6765\u5904\u7406\u67e5\u8be2\u7247\u6bb5\uff0c\u4ece\u800c\u627e\u5230\u5408\u683c\u7684\u884c<\/p>\n<p>\u25e6&lt;ref\/_null\/_helper&gt;(expr)\uff1a\u8fd9\u662f\u4e00\u4e2a\u5185\u90e8\u4f18\u5316\u5668\u5bf9\u8c61\uff0c\u5bf9\u7528\u6237\u6ca1\u6709\u4efb\u4f55\u610f\u4e49<\/p>\n<p>\u25e6\/* select#N *\/ select_stmt\uff1aSELECT\u4e0e\u975e\u6269\u5c55\u7684EXPLAIN\u8f93\u51fa\u4e2did=N\u7684\u90a3\u884c\u5173\u8054<\/p>\n<p>\u25e6outer\/_tables semi join (inner\/_tables)\uff1a\u534a\u8fde\u63a5\u64cd\u4f5c\u3002inner_tables\u5c55\u793a\u672a\u62c9\u51fa\u7684\u8868\u3002\u8be6\u89c1 \u201cOptimizing Subqueries, Derived Tables, and View References with Semijoin Transformations\u201d<\/p>\n<p>\u25e6&lt;temporary table&gt;\uff1a\u8868\u793a\u521b\u5efa\u4e86\u5185\u90e8\u4e34\u65f6\u8868\u800c\u7f13\u5b58\u4e2d\u95f4\u7ed3\u679c<\/p>\n<ul>\n<li>\u5f53\u67d0\u4e9b\u8868\u662fconst\u6216system\u7c7b\u578b\u65f6\uff0c\u8fd9\u4e9b\u8868\u4e2d\u7684\u5217\u6240\u6d89\u53ca\u7684\u8868\u8fbe\u5f0f\u5c06\u7531\u4f18\u5316\u5668\u5c3d\u65e9\u8bc4\u4f30\uff0c\u5e76\u4e14\u4e0d\u5c5e\u4e8e\u6240\u663e\u793a\u8bed\u53e5\u7684\u4e00\u90e8\u5206\u3002\u4f46\u662f\uff0c\u5f53\u4f7f\u7528FORMAT=JSON\u65f6\uff0c\u67d0\u4e9bconst\u8868\u7684\u8bbf\u95ee\u5c06\u663e\u793a\u4e3aref\u3002<\/li>\n<\/ul>\n<h2>5. \u4f30\u8ba1\u67e5\u8be2\u6027\u80fd<\/h2>\n<ul>\n<li>\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7\u8ba1\u7b97\u78c1\u76d8\u7684\u641c\u7d22\u6b21\u6570\u6765\u4f30\u7b97\u67e5\u8be2\u6027\u80fd\u3002\u5bf9\u4e8e\u6bd4\u8f83\u5c0f\u7684\u8868\uff0c\u901a\u5e38\u53ef\u4ee5\u5728\u4e00\u6b21\u78c1\u76d8\u641c\u7d22\u4e2d\u627e\u5230\u884c\uff08\u56e0\u4e3a\u7d22\u5f15\u53ef\u80fd\u5df2\u7ecf\u88ab\u7f13\u5b58\u4e86\uff09\uff0c\u800c\u5bf9\u4e8e\u66f4\u5927\u7684\u8868\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528B-tree\u7d22\u5f15\u8fdb\u884c\u4f30\u7b97\uff1a\u4f60\u9700\u8981\u8fdb\u884c\u591a\u5c11\u6b21\u67e5\u627e\u624d\u80fd\u627e\u5230\u884c\uff1alog(row\/_count) \/ log(index\/_block\/_length \/ 3 * 2 \/ (index\/_length + data\/_pointer\/_length)) + 1<\/li>\n<li>\u5728MySQL\u4e2d\uff0cindex\/_block\/_length\u901a\u5e38\u662f1024\u5b57\u8282\uff0c\u6570\u636e\u6307\u9488\u4e00\u822c\u662f4\u5b57\u8282\u3002\u6bd4\u65b9\u8bf4\uff0c\u6709\u4e00\u4e2a500,000\u7684\u8868\uff0ckey\u662f3\u5b57\u8282\uff0c\u90a3\u4e48\u6839\u636e\u8ba1\u7b97\u516c\u5f0f log(500,000)\/log(1024\/3*2\/(3+4)) + 1 = 4 \u6b21\u641c\u7d22\u3002<\/li>\n<li>\u8be5\u7d22\u5f15\u5c06\u9700\u8981500,000 <em> 7 <\/em> 3\/2 = 5.2MB\u7684\u5b58\u50a8\u7a7a\u95f4\uff08\u5047\u8bbe\u5178\u578b\u7684\u7d22\u5f15\u7f13\u5b58\u7684\u586b\u5145\u7387\u662f2\/3\uff09\uff0c\u56e0\u6b64\u4f60\u53ef\u4ee5\u5728\u5185\u5b58\u4e2d\u5b58\u653e\u66f4\u591a\u7d22\u5f15\uff0c\u53ef\u80fd\u53ea\u8981\u4e00\u5230\u4e24\u4e2a\u8c03\u7528\u5c31\u53ef\u4ee5\u627e\u5230\u60f3\u8981\u7684\u884c\u4e86\u3002<\/li>\n<li>\u4f46\u662f\uff0c\u5bf9\u4e8e\u5199\u64cd\u4f5c\uff0c\u4f60\u9700\u8981\u56db\u4e2a\u641c\u7d22\u8bf7\u6c42\u6765\u67e5\u627e\u5728\u4f55\u5904\u653e\u7f6e\u65b0\u7684\u7d22\u5f15\u503c\uff0c\u7136\u540e\u901a\u5e38\u9700\u89812\u6b21\u641c\u7d22\u6765\u66f4\u65b0\u7d22\u5f15\u5e76\u5199\u5165\u884c\u3002<\/li>\n<li>\u524d\u9762\u7684\u8ba8\u8bba\u5e76\u4e0d\u610f\u5473\u7740\u4f60\u7684\u5e94\u7528\u6027\u80fd\u4f1a\u56e0\u4e3alog N\u800c\u7f13\u6162\u4e0b\u964d\u3002\u53ea\u8981\u5185\u5bb9\u88abOS\u6216MySQL\u670d\u52a1\u5668\u7f13\u5b58\uff0c\u968f\u7740\u8868\u7684\u53d8\u5927\uff0c\u53ea\u4f1a\u7a0d\u5fae\u53d8\u6162\u3002\u5728\u6570\u636e\u91cf\u53d8\u5f97\u592a\u5927\u800c\u65e0\u6cd5\u7f13\u5b58\u540e\uff0c\u5c06\u4f1a\u53d8\u6162\u5f88\u591a\uff0c\u76f4\u5230\u4f60\u7684\u5e94\u7528\u7a0b\u5e8f\u53d7\u5230\u78c1\u76d8\u641c\u7d22\u7ea6\u675f\uff08\u6309\u7167log N\u589e\u957f\uff09\u3002\u4e3a\u4e86\u907f\u514d\u8fd9\u79cd\u60c5\u51b5\uff0c\u53ef\u4ee5\u6839\u636e\u6570\u636e\u7684\u589e\u957f\u800c\u589e\u52a0key\u7684\u3002\u5bf9\u4e8eMyISAM\u8868\uff0ckey\u7684\u7f13\u5b58\u5927\u5c0f\u7531\u540d\u4e3akey\/_buffer\/_size\u7684\u7cfb\u7edf\u53d8\u91cf\u63a7\u5236\uff0c\u8be6\u89c1Section 5.1.1, \u201cConfiguring the Server\u201d<\/li>\n<\/ul>\n<h2>6. \u53c2\u8003\u6587\u6863<\/h2>\n<ul>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=RogM8wkGDKR4utgFNQRLHg%3D%3D.8KgFRZ6rrvdHvCGMP8R%2BnRIwvYgzcvQcq%2F%2BczwNk94TtATOFvsDnmb3pgt2SP9ucuZ%2Bqyoe8RcLN%2FpfIuVfR%2BQ%3D%3D\" rel=\"noopener noreferrer\">EXPLAIN Output Format<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=pQOBlpx%2B0BIHrITJPvhmxQ%3D%3D.6a%2BZa0jz%2BZFDVr4CMo2uLu%2FhVVYSUF3zk4fhN9Y9Q9LbdJGSYY8rvzqSk2IVvmdIIu8EqRSp7CKTT31tDXH5fA%3D%3D\" rel=\"noopener noreferrer\">EXPLAIN Statement<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=L1ToS2kq5%2FXKzkjlYpE5Ag%3D%3D.q8%2FOZu2p9eq1MD7RHmd81F4to6DwDQUJyNIIbuQHFMkGX%2FurOo67iKY%2FvGHlaaMaemc1JBSxOtXsN3bI2AOpvA%3D%3D\" rel=\"noopener noreferrer\">Extended EXPLAIN Output Format<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=3%2F4n9a09J2r4Mpg4reiPeQ%3D%3D.o6TGLBxKo5YywgrllayAJYVKqYgcmu4BXM47CbONV1RrwfruSXPaey7KMTFO%2BCvX0nW%2BmgS9l6x6Vrh1D89uTaC0A%2FKS3CftUJNENlhue1I%3D\" rel=\"noopener noreferrer\">Estimating Query Performance<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=gKfE34GJoXInph412J2fnA%3D%3D.nAO9z2V72BevrREB3aYInwCZ%2FTFAcl1EiKxgm9LnSdKk6VZHIzd8J9ULRGOPpCa74ZRgN4QGNQxN7bNNaWlHTw%3D%3D\" rel=\"noopener noreferrer\">MySQL\u4e2dexplain\u6267\u884c\u8ba1\u5212\u4e2d\u989d\u5916\u4fe1\u606f\u5b57\u6bb5(Extra)\u8be6\u89e3<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=19e54b7A%2ByxWCK7qVmYNAg%3D%3D.W8Ic4TCzwcaK0qFLoIaHKBqIcXjOFL7fCx0OhG7EwPMuCi4uLKRUCtMmeNxGwsMj6%2FrdMoJlYXyVsDon6gNwpQ%3D%3D\" rel=\"noopener noreferrer\">explain\u53c2\u6570\u8be6\u89e3<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=0iu6On2%2Fu2ztZvSkdp8rFw%3D%3D.1hR8WPRdTBVRyiZ%2B5ZO568VQz9068sN1iLMdZqXbz%2FA%3D\" rel=\"noopener noreferrer\">\u6700\u5b98\u65b9\u7684 mysql explain type \u5b57\u6bb5\u89e3\u8bfb<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=rTO%2BgfCs7SaP2u%2FNqPn7Ew%3D%3D.KfIQMq4hgXhczWvVqzZp1tJ0Yo85KZ2P%2FL%2BMVeBnTgmbZP9lVN9t3pP1BWJdV7knYIX8OC1ThKj53Db9Fjiq24wvEmbQqqHMKJiGNxz36u1l9nlyrv6XMzVh8i6tLnU%2BeueaStVW2MvbaYjoYmyN%2Bw%3D%3D\" rel=\"noopener noreferrer\">What does eq_ref and ref types mean in MySQL explain<\/a><\/li>\n<li><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=BPnTuFHwYuDb7q5yFNH6SA%3D%3D.VBqESs3shPv8%2Fh0BzrilJXTWkEe7aghU2qbTdpv3SnSAjpGjI9HXrIXE1bm06zJ1vZglK6ptKvboALvyfTTJQQ%3D%3D\" rel=\"noopener noreferrer\">\u9762\u8bd5\u5b98\uff1a\u4e0d\u4f1a\u770b Explain\u6267\u884c\u8ba1\u5212\uff0c\u7b80\u5386\u6562\u5199 SQL \u4f18\u5316\uff1f<\/a><\/li>\n<\/ul>\n<blockquote>\n<p>\u4f5c\u8005\uff1a\u4eac\u4e1c\u7269\u6d41 \u67f3\u5b8f<\/p>\n<p>\u6765\u6e90\uff1a\u4eac\u4e1c\u4e91\u5f00\u53d1\u8005\u793e\u533a \u81ea\u733f\u5176\u8bf4Tech\u00a0 \u00a0\u8f6c\u8f7d\u8bf7\u6ce8\u660e\u6765\u6e90<\/p>\n<\/blockquote>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000044113745\">https:\/\/segmentfault.com\/a\/1190000044113745<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1. EXPLAIN\u8be6\u89e3 \u672c\u6587\u57fa\u4e8eMySQL 8.0\u7f16\u5199\uff0c\u7406\u8bba\u652f\u6301MySQL 5.0\u53ca\u66f4\u9ad8\u7248\u672c\u3002 2. EXP [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10008093","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008093","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10008093"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008093\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10008093"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10008093"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10008093"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}