https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8zh-cnhttps://blog.youkuaiyun.com/https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137949https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137949o67f2wpkvdf3bpe8Sat, 10 Jun 2023 07:41:41 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137948https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137948o67f2wpkvdf3bpe8Sat, 10 Jun 2023 07:40:49 +0800，>=，BETWEEN，IN，以及某些时候的LIKE才会使用索引。如果分别在 usernname，city，age上建立单列索引，让该表有3个单列索引，查询时和上述的组合索引效率也会大不一样，远远低于我们的组合索引。例如，如果有一个CHAR(255)的列，如果在前10个或20个字符内，多数值是惟一的，那么就不要对整个列进行索引。因为更新表时，MySQL不仅要保存数据，还要保存一下索引文件。]]>https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137946https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137946o67f2wpkvdf3bpe8Sat, 10 Jun 2023 07:37:28 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137934https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137934o67f2wpkvdf3bpe8Sat, 10 Jun 2023 07:37:09 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137924https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/131137924o67f2wpkvdf3bpe8Sat, 10 Jun 2023 07:27:09 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/130097741https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/130097741o67f2wpkvdf3bpe8Wed, 12 Apr 2023 06:16:50 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/130097737https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/130097737o67f2wpkvdf3bpe8Wed, 12 Apr 2023 06:06:52 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828915https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828915o67f2wpkvdf3bpe8Wed, 29 Mar 2023 07:43:08 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828912https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828912o67f2wpkvdf3bpe8Wed, 29 Mar 2023 07:39:09 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828905https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828905o67f2wpkvdf3bpe8Wed, 29 Mar 2023 07:33:25 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828903https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828903o67f2wpkvdf3bpe8Wed, 29 Mar 2023 07:33:09 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828887https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129828887o67f2wpkvdf3bpe8Wed, 29 Mar 2023 07:23:57 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129700058https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129700058o67f2wpkvdf3bpe8Tue, 21 Mar 2023 23:27:05 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129484002https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129484002o67f2wpkvdf3bpe8Mon, 13 Mar 2023 01:58:25 +0800https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129392624https://blog.youkuaiyun.com/o67f2wpkvdf3bpe8/article/details/129392624o67f2wpkvdf3bpe8Tue, 07 Mar 2023 22:01:12 +0800