创建用户：
create user ‘test’@’%’ identified by ‘test’;
显示ERROR 1396 (HY000): Operation CREATE USER failed for ‘test’@’%’
查看是不是存在这个用户
select user from user;
发现没有这个用户。
记得上次有删除过这个用户。可能没有刷新权限
flush privileges;
之后还是不行报错ERROR 1396 (HY000): Operation CREATE USER failed for ‘test’@’%’
没办法再删除一次：
drop user ‘test’@’%’;
flush privileges;
之后create user ‘test’@’%’ identified by ‘test’;
成功。
网上找了下原因：
Assume the user is there, so drop the user
After deleting the user, there is need to flush the mysql privileges
Now create the user.
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