在mysql自带的库中有一个mysql，这个库包含了太多的东西，其中有一张表user，这张表存储了所有的用户信息。
mysql> select user,host,password from user; +------+-----------------------+-------------------------------------------+ | user | host | password | +------+-----------------------+-------------------------------------------+ | root | localhost | *E01F5425C006D5AF5E3E22EEF9D6AF6BD19FDFED | | root | localhost.localdomain | | | root | 127.0.0.1 | | | root | ::1 | | | | localhost | | | | localhost.localdomain | | +------+-----------------------+-------------------------------------------+ 6 rows in set (0.00 sec)