{"id":30679,"date":"2023-05-19T17:01:23","date_gmt":"2023-05-19T09:01:23","guid":{"rendered":"https:\/\/docs.pingcode.com\/?p=30679"},"modified":"2023-07-31T00:01:45","modified_gmt":"2023-07-30T16:01:45","slug":"mysql%e7%9a%84%e8%a6%86%e7%9b%96%e7%b4%a2%e5%bc%95%e5%92%8c%e8%81%94%e5%90%88%e7%b4%a2%e5%bc%95%e7%9a%84%e5%8c%ba%e5%88%ab%e5%9c%a8%e5%93%aa%e9%87%8c","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/30679.html","title":{"rendered":"Mysql\u7684\u8986\u76d6\u7d22\u5f15\u548c\u8054\u5408\u7d22\u5f15\u7684\u533a\u522b\u5728\u54ea\u91cc"},"content":{"rendered":"
\n

\u8054\u5408\u7d22\u5f15\u65f6\u6307\u5bf9\u8868\u4e0a\u7684\u591a\u4e2a\u5217\u5408\u8d77\u6765\u505a\u4e00\u4e2a\u7d22\u5f15\u3002\u8054\u5408\u7d22\u5f15\u7684\u521b\u5efa\u65b9\u6cd5\u4e0e\u5355\u4e2a\u7d22\u5f15\u7684\u521b\u5efa\u65b9\u6cd5\u4e00\u6837\uff1bInnoDB\u5b58\u50a8\u5f15\u64ce\u652f\u6301\u8986\u76d6\u7d22\u5f15\uff08covering index\uff0c\u6216\u79f0\u7d22\u5f15\u8986\u76d6\uff09\uff0c\u5373\u4ece\u8f85\u52a9\u7d22\u5f15\u4e2d\u5c31\u53ef\u4ee5\u5f97\u5230\u67e5\u8be2\u8bb0\u5f55\u3002<\/p>\n<\/blockquote>\n

\n
\"\"<\/figure>\n<\/div>\n

\u4e00\u3001Mysql\u7684\u8986\u76d6\u7d22\u5f15\u548c\u8054\u5408\u7d22\u5f15\u7684\u533a\u522b<\/strong><\/h2>\n

\u8054\u5408\u7d22\u5f15<\/strong><\/h3>\n
    \n
  • \u8054\u5408\u7d22\u5f15\u65f6\u6307\u5bf9\u8868\u4e0a\u7684\u591a\u4e2a\u5217\u5408\u8d77\u6765\u505a\u4e00\u4e2a\u7d22\u5f15\u3002\u8054\u5408\u7d22\u5f15\u7684\u521b\u5efa\u65b9\u6cd5\u4e0e\u5355\u4e2a\u7d22\u5f15\u7684\u521b\u5efa\u65b9\u6cd5\u4e00\u6837\uff0c\u4e0d\u540c\u4e4b\u5904\u5728\u4ec5\u5728\u4e8e\u6709\u591a\u4e2a\u7d22\u5f15\u5217\uff0c\u5982\u4e0b<\/li>\n<\/ul>\n

    mysql> create table t(<\/p>\n

    \u00a0\u00a0\u00a0 -> a int,<\/p>\n

    \u00a0\u00a0\u00a0 -> b int,<\/p>\n

    \u00a0\u00a0\u00a0 -> primary key(a),<\/p>\n

    \u00a0\u00a0\u00a0 -> key idx_a_b(a,b)<\/p>\n

    \u00a0\u00a0\u00a0 -> );<\/p>\n

    Query OK, 0 rows affected (0.11 sec)<\/p>\n

      \n
    • \u90a3\u4e48\u4f55\u65f6\u9700\u8981\u4f7f\u7528\u8054\u5408\u7d22\u5f15\u5462\uff1f\u5728\u8ba8\u8bba\u8fd9\u4e2a\u95ee\u9898\u4e4b\u524d\uff0c\u5148\u6765\u770b\u4e00\u4e0b\u8054\u5408\u7d22\u5f15\u5185\u90e8\u7684\u7ed3\u679c\u3002\u4ece\u672c\u8d28\u4e0a\u6765\u8bf4\uff0c\u8054\u5408\u7d22\u5f15\u5c31\u662f\u4e00\u68f5B+\u6811\uff0c\u4e0d\u540c\u7684\u662f\u8054\u5408\u7d22\u5f15\u7684\u952e\u503c\u5f97\u6570\u91cf\u4e0d\u662f1\uff0c\u800c\u662f>=2\u3002\u63a5\u7740\u6765\u8ba8\u8bba\u4e24\u4e2a\u6574\u578b\u5217\u7ec4\u6210\u7684\u8054\u5408\u7d22\u5f15\uff0c\u5047\u5b9a\u4e24\u4e2a\u952e\u503c\u5f97\u540d\u79f0\u5206\u522b\u4e3aa\u3001b\u5982\u56fe<\/li>\n<\/ul>\n
        \n
      • \u53ef\u4ee5\u770b\u5230\u8fd9\u4e0e\u6211\u4eec\u4e4b\u524d\u770b\u5230\u7684\u5355\u4e2a\u952e\u7684B+\u6811\u5e76\u6ca1\u6709\u4ec0\u4e48\u4e0d\u540c\uff0c\u952e\u503c\u90fd\u662f\u6392\u5e8f\u7684\uff0c\u901a\u8fc7\u53f6\u5b50\u7ed3\u70b9\u53ef\u4ee5\u903b\u8f91\u4e0a\u987a\u5e8f\u5730\u8bfb\u51fa\u6240\u6709\u6570\u636e\uff0c\u5c31\u4e0a\u9762\u7684\u4f8b\u5b50\u6765\u8bf4\uff0c\u5373\uff081,1\uff09\uff0c\uff081,2\uff09\uff0c\uff082,1\uff09\uff0c\uff082,4\uff09\uff0c\uff083,1\uff09\uff0c\uff083,2\uff09\uff0c\u6570\u636e\u6309\uff08a,b\uff09\u7684\u987a\u5e8f\u8fdb\u884c\u4e86\u5b58\u653e\u3002<\/li>\n
      • \u56e0\u6b64\uff0c\u5bf9\u4e8e\u67e5\u8be2select * from table where a=xxx and b=xxx, \u663e\u7136\u662f\u53ef\u4ee5\u4f7f\u7528(a,b) \u8fd9\u4e2a\u8054\u5408\u7d22\u5f15\u7684\uff0c\u5bf9\u4e8e\u5355\u4e2a\u5217a\u7684\u67e5\u8be2select * from table where a=xxx,\u4e5f\u662f\u53ef\u4ee5\u4f7f\u7528\uff08a,b\uff09\u8fd9\u4e2a\u7d22\u5f15\u7684\u3002<\/li>\n
      • \u4f46\u5bf9\u4e8eb\u5217\u7684\u67e5\u8be2select * from table where b=xxx,\u5219\u4e0d\u53ef\u4ee5\u4f7f\u7528\uff08a,b\uff09 \u7d22\u5f15\uff0c\u5176\u5b9e\u4f60\u4e0d\u96be\u53d1\u73b0\u539f\u56e0\uff0c\u53f6\u5b50\u8282\u70b9\u4e0ab\u7684\u503c\u4e3a1\u30012\u30011\u30014\u30011\u30012\u663e\u7136\u4e0d\u662f\u6392\u5e8f\u7684\uff0c\u56e0\u6b64\u5bf9\u4e8eb\u5217\u7684\u67e5\u8be2\u4f7f\u7528\u4e0d\u5230(a,b) \u7d22\u5f15<\/li>\n
      • \u8054\u5408\u7d22\u5f15\u7684\u7b2c\u4e8c\u4e2a\u597d\u5904\u662f\u5728\u540d\u5217\u524d\u8305\u4e2a\u952e\u76f8\u540c\u7684\u60c5\u51b5\u4e0b\uff0c\u5df2\u7ecf\u5bf9\u7b2c\u4e8c\u4e2a\u952e\u8fdb\u884c\u4e86\u6392\u5e8f\u5904\u7406\uff0c\u4f8b\u5982\u5728\u5f88\u591a\u60c5\u51b5\u4e0b\u5e94\u7528\u7a0b\u5e8f\u90fd\u9700\u8981\u67e5\u8be2\u67d0\u4e2a\u7528\u6237\u7684\u8d2d\u7269\u60c5\u51b5\uff0c\u5e76\u6309\u7167\u65f6\u95f4\u8fdb\u884c\u6392\u5e8f\uff0c\u6700\u540e\u53d6\u51fa\u6700\u8fd1\u4e09\u6b21\u7684\u8d2d\u4e70\u8bb0\u5f55\uff0c\u8fd9\u65f6\u4f7f\u7528\u8054\u5408\u7d22\u5f15\u53ef\u4ee5\u5e2e\u6211\u4eec\u907f\u514d\u591a\u4e00\u6b21\u7684\u6392\u5e8f\u64cd\u4f5c\uff0c\u56e0\u4e3a\u7d22\u5f15\u672c\u8eab\u5728\u53f6\u5b50\u8282\u70b9\u5df2\u7ecf\u6392\u5e8f\u4e86\uff0c\u5982\u4e0b<\/li>\n<\/ul>\n

        #===========\u51c6\u5907\u8868==============<\/p>\n

        create table buy_log(<\/p>\n

        \u00a0\u00a0\u00a0 userid int unsigned not null,<\/p>\n

        \u00a0\u00a0\u00a0 buy_date date<\/p>\n

        );<\/p>\n

        insert into buy_log values<\/p>\n

        (1,\u20192009-01-01\u2032),<\/p>\n

        (2,\u20192009-01-01\u2032),<\/p>\n

        (3,\u20192009-01-01\u2032),<\/p>\n

        (1,\u20192009-02-01\u2032),<\/p>\n

        (3,\u20192009-02-01\u2032),<\/p>\n

        (1,\u20192009-03-01\u2032),<\/p>\n

        (1,\u20192009-04-01\u2032);<\/p>\n

        alter table buy_log add key(userid);<\/p>\n

        alter table buy_log add key(userid,buy_date);<\/p>\n

        #===========\u9a8c\u8bc1==============<\/p>\n

        mysql> show create table buy_log;<\/p>\n

        | buy_log | CREATE TABLE `buy_log` (<\/p>\n

        \u00a0 `userid` int(10) unsigned NOT NULL,<\/p>\n

        \u00a0 `buy_date` date DEFAULT NULL,<\/p>\n

        \u00a0 KEY `userid` (`userid`),<\/p>\n

        \u00a0 KEY `userid_2` (`userid`,`buy_date`)<\/p>\n

        ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |<\/p>\n

        #\u53ef\u4ee5\u770b\u5230possible_keys\u5728\u8fd9\u91cc\u6709\u4e24\u4e2a\u7d22\u5f15\u53ef\u4ee5\u7528\uff0c\u5206\u522b\u662f\u5355\u4e2a\u7d22\u5f15userid\u4e0e\u8054\u5408\u7d22\u5f15userid_2,\u4f46\u662f\u4f18\u5316\u5668\u6700\u7ec8\u9009\u62e9\u4e86\u4f7f\u7528\u7684key\u662fuserid\u56e0\u4e3a\u8be5\u7d22\u5f15\u7684\u53f6\u5b50\u8282\u70b9\u5305\u542b\u5355\u4e2a\u952e\u503c\uff0c\u6240\u4ee5\u7406\u8bba\u4e0a\u4e00\u4e2a\u9875\u80fd\u5b58\u653e\u7684\u8bb0\u5f55\u5e94\u8be5\u66f4\u591a<\/p>\n

        mysql> explain select * from buy_log where userid=2;<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2013+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014-+<\/p>\n

        | id | select_type | table\u00a0\u00a0 | type | possible_keys\u00a0\u00a0 | key\u00a0\u00a0\u00a0 | key_len | ref\u00a0\u00a0 | rows | Extra |<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2013+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014-+<\/p>\n

        |\u00a0 1 | SIMPLE\u00a0\u00a0\u00a0\u00a0\u00a0 | buy_log | ref\u00a0 | userid,userid_2 | userid | 4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | const |\u00a0\u00a0\u00a0 1 |\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 |<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2013+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014-+<\/p>\n

        1 row in set (0.00 sec)<\/p>\n

        #\u63a5\u7740\u5047\u5b9a\u8981\u53d6\u51fauserid\u4e3a1\u7684\u6700\u8fd13\u6b21\u7684\u8d2d\u4e70\u8bb0\u5f55\uff0c\u7528\u7684\u5c31\u662f\u8054\u5408\u7d22\u5f15userid_2\u4e86\uff0c\u56e0\u4e3a\u5728\u8fd9\u4e2a\u7d22\u5f15\u4e2d\uff0c\u5728userid=1\u7684\u60c5\u51b5\u4e0b\uff0cbuy_date\u90fd\u5df2\u7ecf\u6392\u5e8f\u597d\u4e86<\/p>\n

        mysql> explain select * from buy_log where userid=1 order by buy_date desc limit 3;<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2013+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

        | id | select_type | table\u00a0\u00a0 | type | possible_keys\u00a0\u00a0 | key\u00a0\u00a0\u00a0\u00a0\u00a0 | key_len | ref\u00a0\u00a0 | rows | Extra\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 |<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2013+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

        |\u00a0 1 | SIMPLE\u00a0\u00a0\u00a0\u00a0\u00a0 | buy_log | ref\u00a0 | userid,userid_2 | userid_2 | 4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | const |\u00a0\u00a0\u00a0 4 | Using where; Using index |<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2013+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

        1 row in set (0.00 sec)<\/p>\n

        #ps\uff1a\u5982\u679cextra\u7684\u6392\u5e8f\u663e\u793a\u662fUsing filesort\uff0c\u5219\u610f\u5473\u7740\u5728\u67e5\u51fa\u6570\u636e\u540e\u9700\u8981\u4e8c\u6b21\u6392\u5e8f(\u5982\u4e0b\u67e5\u8be2\u8bed\u53e5\uff0c\u6ca1\u6709\u5148\u7528where userid=3\u5148\u5b9a\u4f4d\u8303\u56f4\uff0c\u4e8e\u662f\u5373\u4fbf\u547d\u4e2d\u7d22\u5f15\u4e5f\u6ca1\u7528\uff0c\u9700\u8981\u4e8c\u6b21\u6392\u5e8f)<\/p>\n

        mysql> explain select * from buy_log order by buy_date desc limit 3;<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

        | id | select_type | table\u00a0\u00a0 | type\u00a0 | possible_keys | key\u00a0\u00a0\u00a0\u00a0\u00a0 | key_len | ref\u00a0 | rows | Extra\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 |<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

        |\u00a0 1 | SIMPLE\u00a0\u00a0\u00a0\u00a0\u00a0 | buy_log | index | NULL\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | userid_2 | 8\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | NULL |\u00a0\u00a0\u00a0 7 | Using index; Using filesort |<\/p>\n

        +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

        #\u5bf9\u4e8e\u8054\u5408\u7d22\u5f15\uff08a,b\uff09,\u4e0b\u8ff0\u8bed\u53e5\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u8be5\u7d22\u5f15\uff0c\u65e0\u9700\u4e8c\u6b21\u6392\u5e8f<\/p>\n

        select \u2026 from table where a=xxx order by b;<\/p>\n

        #\u7136\u540e\u5bf9\u4e8e\u8054\u5408\u7d22\u5f15(a,b,c)\u6765\u9996\uff0c\u4e0b\u5217\u8bed\u53e5\u540c\u6837\u53ef\u4ee5\u76f4\u63a5\u901a\u8fc7\u7d22\u5f15\u5f97\u5230\u7ed3\u679c<\/p>\n

        select \u2026 from table where a=xxx order by b;<\/p>\n

        select \u2026 from table where a=xxx and b=xxx order by c;<\/p>\n

        #\u4f46\u662f\u5bf9\u4e8e\u8054\u5408\u7d22\u5f15(a,b,c)\uff0c\u4e0b\u5217\u8bed\u53e5\u4e0d\u80fd\u901a\u8fc7\u7d22\u5f15\u76f4\u63a5\u5f97\u5230\u7ed3\u679c\uff0c\u8fd8\u9700\u8981\u81ea\u5df1\u6267\u884c\u4e00\u6b21filesort\u64cd\u4f5c\uff0c\u56e0\u4e3a\u7d22\u5f15\uff08a\uff0cc)\u5e76\u672a\u6392\u5e8f<\/p>\n

        select \u2026 from table where a=xxx order by c;<\/p>\n

        \u8986\u76d6\u7d22\u5f15<\/strong><\/h3>\n

        InnoDB\u5b58\u50a8\u5f15\u64ce\u652f\u6301\u8986\u76d6\u7d22\u5f15\uff08covering index\uff0c\u6216\u79f0\u7d22\u5f15\u8986\u76d6\uff09\uff0c\u5373\u4ece\u8f85\u52a9\u7d22\u5f15\u4e2d\u5c31\u53ef\u4ee5\u5f97\u5230\u67e5\u8be2\u8bb0\u5f55\uff0c\u800c\u4e0d\u9700\u8981\u67e5\u8be2\u805a\u96c6\u7d22\u5f15\u4e2d\u7684\u8bb0\u5f55\u3002<\/p>\n

          \n
        • \u4f7f\u7528\u8986\u76d6\u7d22\u5f15\u7684\u4e00\u4e2a\u597d\u5904\u662f\uff1a\u8f85\u52a9\u7d22\u5f15\u4e0d\u5305\u542b\u6574\u884c\u8bb0\u5f55\u7684\u6240\u6709\u4fe1\u606f\uff0c\u6545\u5176\u5927\u5c0f\u8981\u8fdc\u5c0f\u4e8e\u805a\u96c6\u7d22\u5f15\uff0c\u56e0\u6b64\u53ef\u4ee5\u51cf\u5c11\u5927\u91cf\u7684IO\u64cd\u4f5c<\/li>\n
        • \u6ce8\u610f\uff1a\u8986\u76d6\u7d22\u5f15\u6280\u672f\u8f83\u65e9\u662f\u5728InnoDB Plugin\u4e2d\u5b8c\u6210\u5e76\u5b9e\u73b0\uff0c\u8fd9\u610f\u5473\u7740\u5bf9\u4e8eInnoDB\u7248\u672c\u5c0f\u4e8e1.0\u7684\uff0c\u6216\u8005MySQL\u6570\u636e\u5e93\u7248\u672c\u4e3a5.0\u4ee5\u4e0b\u7684\uff0cInnoDB\u5b58\u50a8\u5f15\u64ce\u4e0d\u652f\u6301\u8986\u76d6\u7d22\u5f15\u7279\u6027<\/li>\n
        • \u5bf9\u4e8eInnoDB\u5b58\u50a8\u5f15\u64ce\u7684\u8f85\u52a9\u7d22\u5f15\u800c\u8a00\uff0c\u7531\u4e8e\u5176\u5305\u542b\u4e86\u4e3b\u952e\u4fe1\u606f\uff0c\u56e0\u6b64\u5176\u53f6\u5b50\u8282\u70b9\u5b58\u653e\u7684\u6570\u636e\u4e3a\uff08primary key1\uff0cpriamey key2\uff0c\u2026,key1\uff0ckey2\uff0c\u2026\uff09\u3002\u4f8b\u5982<\/li>\n<\/ul>\n

          select age from s1 where id=123 and name = \u2018wot\u2019; #id\u5b57\u6bb5\u6709\u7d22\u5f15\uff0c\u4f46\u662fname\u5b57\u6bb5\u6ca1\u6709\u7d22\u5f15,\u8be5sql\u547d\u4e2d\u4e86\u7d22\u5f15\uff0c\u4f46\u672a\u8986\u76d6\uff0c\u9700\u8981\u53bb\u805a\u96c6\u7d22\u5f15\u4e2d\u518d\u67e5\u627e\u8be6\u7ec6\u4fe1\u606f\u3002<\/p>\n

          \u6700\u725b\u903c\u7684\u60c5\u51b5\u662f\uff0c\u7d22\u5f15\u5b57\u6bb5\u8986\u76d6\u4e86\u6240\u6709\uff0c\u90a3\u5168\u7a0b\u901a\u8fc7\u7d22\u5f15\u6765\u52a0\u901f\u67e5\u8be2\u4ee5\u53ca\u83b7\u53d6\u7ed3\u679c\u5c31ok\u4e86<\/p>\n

          mysql> desc s1;<\/p>\n

          +\u2014\u2014\u2013+\u2014\u2014\u2014\u2014-+\u2014\u2014+\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+<\/p>\n

          | Field | Type | Null | Key | Default | Extra |<\/p>\n

          +\u2014\u2014\u2013+\u2014\u2014\u2014\u2014-+\u2014\u2014+\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+<\/p>\n

          | id\u00a0\u00a0\u00a0 | int(11) | NO |\u00a0\u00a0\u00a0 | NULL\u00a0\u00a0\u00a0 |\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 |<\/p>\n

          | name | varchar(20) | YES | | NULL | |<\/p>\n

          | gender | char(6) | YES | | NULL | |<\/p>\n

          | email | varchar(50) | YES | | NULL | |<\/p>\n

          +\u2014\u2014\u2013+\u2014\u2014\u2014\u2014-+\u2014\u2014+\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+<\/p>\n

          4 rows in set (0.21 sec)<\/p>\n

          mysql> explain select name from s1 where id=1000; #\u6ca1\u6709\u4efb\u4f55\u7d22\u5f15<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014\u2014-+<\/p>\n

          | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014\u2014-+<\/p>\n

          | 1 | SIMPLE | s1 | NULL | ALL | NULL | NULL | NULL | NULL | 2688336 | 10.00 | Using where |<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014\u2014-+<\/p>\n

          1 row in set, 1 warning (0.00 sec)<\/p>\n

          mysql> create index idx_id on s1(id); #\u521b\u5efa\u7d22\u5f15<\/p>\n

          Query OK, 0 rows affected (4.16 sec)<\/p>\n

          Records: 0 Duplicates: 0 Warnings: 0<\/p>\n

          mysql> explain select name from s1 where id=1000; #\u547d\u4e2d\u8f85\u52a9\u7d22\u5f15\uff0c\u4f46\u662f\u672a\u8986\u76d6\u7d22\u5f15\uff0c\u8fd8\u9700\u8981\u4ece\u805a\u96c6\u7d22\u5f15\u4e2d\u67e5\u627ename<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014-+<\/p>\n

          | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014-+<\/p>\n

          | 1 | SIMPLE | s1 | NULL | ref | idx_id | idx_id | 4 | const | 1 | 100.00 | NULL |<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014-+<\/p>\n

          1 row in set, 1 warning (0.08 sec)<\/p>\n

          mysql> explain select id from s1 where id=1000; #\u5728\u8f85\u52a9\u7d22\u5f15\u4e2d\u5c31\u627e\u5230\u4e86\u5168\u90e8\u4fe1\u606f\uff0cUsing index\u4ee3\u8868\u8986\u76d6\u7d22\u5f15<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014\u2014-+<\/p>\n

          | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014\u2014-+<\/p>\n

          | 1 | SIMPLE | s1 | NULL | ref | idx_id | idx_id | 4 | const | 1 | 100.00 | Using index |<\/p>\n

          +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014-+\u2014\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014\u2014-+<\/p>\n

          1 row in set, 1 warning (0.03 sec)<\/p>\n

            \n
          • \u8986\u76d6\u7d22\u5f15\u7684\u53e6\u5916\u4e00\u4e2a\u597d\u5904\u662f\u5bf9\u67d0\u4e9b\u7edf\u8ba1\u95ee\u9898\u800c\u8a00\u7684\u3002\u57fa\u4e8e\u4e0a\u4e00\u5c0f\u7ed3\u521b\u5efa\u7684\u8868buy_log,\u67e5\u8be2\u8ba1\u5212\u5982\u4e0b<\/li>\n<\/ul>\n

            mysql> explain select count(*) from buy_log;<\/p>\n

            +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014-+<\/p>\n

            | id | select_type | table\u00a0\u00a0 | type\u00a0 | possible_keys | key\u00a0\u00a0\u00a0 | key_len | ref\u00a0 | rows | Extra\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 |<\/p>\n

            +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014-+<\/p>\n

            |\u00a0 1 | SIMPLE\u00a0\u00a0\u00a0\u00a0\u00a0 | buy_log | index | NULL\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | userid | 4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | NULL |\u00a0\u00a0\u00a0 7 | Using index |<\/p>\n

            +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2013+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014-+<\/strong><\/p>\n

            1 row in<\/strong> set (0.00 sec)<\/p>\n

              \n
            • innodb\u5b58\u50a8\u5f15\u64ce\u5e76\u4e0d\u4f1a\u9009\u62e9\u901a\u8fc7\u67e5\u8be2\u805a\u96c6\u7d22\u5f15\u6765\u8fdb\u884c\u7edf\u8ba1\u3002\u7531\u4e8ebuy_log\u8868\u6709\u8f85\u52a9\u7d22\u5f15\uff0c\u800c\u8f85\u52a9\u7d22\u5f15\u8fdc\u5c0f\u4e8e\u805a\u96c6\u7d22\u5f15\uff0c\u9009\u62e9\u8f85\u52a9\u7d22\u5f15\u53ef\u4ee5\u51cf\u5c11IO\u64cd\u4f5c\uff0c\u6545\u4f18\u5316\u5668\u7684\u9009\u62e9\u5982\u4e0akey\u4e3auserid\u8f85\u52a9\u7d22\u5f15<\/li>\n
            • \u5bf9\u4e8e\uff08a,b\uff09\u5f62\u5f0f\u7684\u8054\u5408\u7d22\u5f15\uff0c\u4e00\u822c\u662f\u4e0d\u53ef\u4ee5\u9009\u62e9b\u4e2d\u6240\u8c13\u7684\u67e5\u8be2\u6761\u4ef6\u3002\u4f46\u5982\u679c\u662f\u7edf\u8ba1\u64cd\u4f5c\uff0c\u5e76\u4e14\u662f\u8986\u76d6\u7d22\u5f15\uff0c\u5219\u4f18\u5316\u5668\u8fd8\u662f\u4f1a\u9009\u62e9\u4f7f\u7528\u8be5\u7d22\u5f15\uff0c\u5982\u4e0b<\/li>\n<\/ul>\n

              #\u8054\u5408\u7d22\u5f15userid_2\uff08userid,buy_date\uff09,\u4e00\u822c\u60c5\u51b5\uff0c\u6211\u4eec\u6309\u7167buy_date\u662f\u65e0\u6cd5\u4f7f\u7528\u8be5\u7d22\u5f15\u7684\uff0c\u4f46\u7279\u6b8a\u60c5\u51b5\u4e0b\uff1a\u67e5\u8be2\u8bed\u53e5\u662f\u7edf\u8ba1\u64cd\u4f5c\uff0c\u4e14\u662f\u8986\u76d6\u7d22\u5f15\uff0c\u5219\u6309\u7167buy_date\u5f53\u505a\u67e5\u8be2\u6761\u4ef6\u65f6\uff0c\u4e5f\u53ef\u4ee5\u4f7f\u7528\u8be5\u8054\u5408\u7d22\u5f15<\/p>\n

              mysql> explain select count(*) from buy_log where buy_date >= \u20182011-01-01\u2019 and buy_date < \u20182011-02-01\u2019;<\/p>\n

              +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

              | id | select_type | table\u00a0\u00a0 | type\u00a0 | possible_keys | key\u00a0\u00a0\u00a0\u00a0\u00a0 | key_len | ref\u00a0 | rows | Extra\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 |<\/p>\n

              +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/p>\n

              |\u00a0 1 | SIMPLE\u00a0\u00a0\u00a0\u00a0\u00a0 | buy_log | index | NULL\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | userid_2 | 8\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 | NULL |\u00a0\u00a0\u00a0 7 | Using where; Using index |<\/p>\n

              +\u2014-+\u2014\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014-+\u2014\u2014\u2014\u2014\u2014+\u2014\u2014\u2014-+\u2014\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2013+<\/strong><\/p>\n

              1 row in set (0.00 sec)<\/p>\n

              \u5ef6\u4f38\u9605\u8bfb\uff1a<\/strong><\/p>\n

              \u4e8c\u3001\u4ec0\u4e48\u662fMemory\u5f15\u64ce<\/strong><\/h2>\n

              Memory\u5f15\u64ce\u662fMysql\u7684\u5185\u5b58\u5f15\u64ce\uff0c\u5728\u5b9e\u73b0\u4e0a\uff0cMemory\u5b58\u50a8\u5f15\u64ce\u4e0d\u540c\u4e8eInnodb\u8fd9\u79cd\u7ec4\u7ec7\u7d22\u5f15\u7ed3\u6784(\u7d22\u5f15\u5373\u662f\u6570\u636e\uff0c\u5373\u6570\u636e\u5b58\u653e\u5728\u4e3b\u952e\u7d22\u5f15\u4e0a)\uff0c\u800c\u662f\u5c06\u7d22\u5f15\u548c\u6570\u636e\u5206\u5f00\u5b58\u50a8\u3002\u7d22\u5f15\u91c7\u7528Hash\u7684\u5f62\u5f0f\uff0c\u5b58\u653e\u4e3b\u952eid\u548c\u6307\u5411\u6570\u636e\u7684\u6307\u9488\uff0c\u800c\u6570\u636e\u5219\u6309\u63d2\u5165\u987a\u5e8f\u5b58\u653e\u3002\u6211\u4eec\u79f0\u8fd9\u79cd\u6570\u636e\u7ec4\u7ec7\u65b9\u5f0f\u4e3a\u5806\u7ec4\u7ec7\u65b9\u5f0f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"\u8054\u5408\u7d22\u5f15\u65f6\u6307\u5bf9\u8868\u4e0a\u7684\u591a\u4e2a\u5217\u5408\u8d77\u6765\u505a\u4e00\u4e2a\u7d22\u5f15\u3002\u8054\u5408\u7d22\u5f15\u7684\u521b\u5efa\u65b9\u6cd5\u4e0e\u5355\u4e2a\u7d22\u5f15\u7684\u521b\u5efa\u65b9\u6cd5\u4e00\u6837\uff1bInnoDB\u5b58\u50a8\u5f15\u64ce\u652f […]","protected":false},"author":1,"featured_media":30680,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[37],"tags":[],"acf":[],"_links":{"self":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/30679"}],"collection":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/comments?post=30679"}],"version-history":[{"count":0,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/30679\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media\/30680"}],"wp:attachment":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media?parent=30679"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/categories?post=30679"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/tags?post=30679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}