账户的创建大概分为：
在MySQL上创建用户：
MariaDB [(none)]> create user first@"localhost" identified by "123456"; Query OK, 0 rows affected (0.001 sec) MariaDB [(none)]> flush privileges; Query OK, 0 rows affected (0.000 sec)
在MySQL上删除用户：
MariaDB [(none)]> Delete FROM mysql.user Where User='first' and Host='localhost';
Query OK, 1 row affected (0.000 sec)
MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.000 sec)
