Mysql实验之使用explain分析索引的走向

DROP TABLE IF EXISTS `qz_users`;
CREATE TABLE `qz_users` (
 `uid` int(11) unsigned NOT NULL AUTO_INCREMENT COMMENT '用户的 UID',
 `user_name` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '用户名',
 `real_name` varchar(128) CHARACTER SET utf8 DEFAULT NULL COMMENT '用户姓名',
 `email` varchar(255) CHARACTER SET utf8 DEFAULT NULL COMMENT 'EMAIL',
 `mobile` varchar(16) CHARACTER SET utf8 DEFAULT NULL COMMENT '用户手机',
 `password` varchar(32) CHARACTER SET utf8 DEFAULT NULL COMMENT '用户密码',
 `salt` varchar(16) CHARACTER SET utf8 DEFAULT NULL COMMENT '用户附加混淆码',
 `avatar_file` varchar(128) CHARACTER SET utf8 DEFAULT NULL COMMENT '头像文件',
 `sex` tinyint(1) DEFAULT NULL COMMENT '性别',
 `birthday` int(10) DEFAULT NULL COMMENT '生日',
 PRIMARY KEY (`uid`),
 KEY `user_name` (`user_name`(250)),
 KEY `complex_index` (`email`,`mobile`,`sex`)
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

explain select * from qz_users where user_name = "ryanhe";
explain select * from qz_users where email = "x";
explain select * from qz_users where email = "x" and mobile = "x" and sex=1;
explain select * from qz_users where email = "x" and mobile = "x";
explain select * from qz_users where email = "x" and sex = "x";
explain select * from qz_users where sex = "x" and mobile = "x";
explain select * from qz_users where mobile = "x" and sex = "0";

explain select * from qz_users where user_name= "x";

explain select * from qz_users where email = "x";

explain select * from qz_users where email = "x" and mobile = "x" and sex=1;

explain select * from qz_users where email = "x" and mobile = "x";

explain select * from qz_users where email = "x" and sex = "x";

explain select * from qz_users where sex = "x" and mobile = "x";

explain select * from qz_users where mobile = "18602199680" and sex = "0";