1.创建用户
mysql> create user 'username'@'localhost/%/ip' identified by 'password';
Query OK, 0 rows affected (0.05 sec)
// 说明 localhost/%/ip ，可以指定ip（限定ip访问），localhost（本服务器访问）以及%（不限制ip访问）
2.赋予权限
mysql> grant select/update/insert/delete/alter/drop/create(能是一个或多个权限) on *.* to 'username'@'localhost/ip/%';
Query OK, 0 rows affected (0.01 sec)
3.删除用户delete和drop两种删除
推荐使用drop以防ERROR 1396 (HY000): Operation CREATE USER failed for 'username'@'password'
方式一：
mysql> delete from user where user='username' and host='localhost';
Query OK, 1 row affected (0.02 sec)
mysql> flush privileges; // 记得刷新权限表，如果不刷新的话，直接创建相同用户会报错。
Query OK, 0 rows affected (0.01 sec)
方式二：
mysql> drop user 'username'@'localhost';
Query OK, 0 rows affected (0.00 sec)
错误：
mysql> delete from user where user='username' and host='localhost';
Query OK, 1 row affected (0.02 sec)
mysql> create user 'username'@'localhost' identified by 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for 'username'@'password'
解决：
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> create user 'username'@'localhost' identified by 'password';
Query OK, 0 rows affected (0.00 sec)
