Error Message:
ERROR 1396 (HY000): Operation CREATE USER failed for 'admin'@'%'
Generic Error Message:
Operation %s failed for %s
Error Scenario:
Operation CREATE USER failedOperation DROP USER failed
Reason:
The reason for this error is, you are trying to do some user operation but the user does not exist on the MySQL system. Also, for drop user, the user details are stored somewhere in the system, even though, you have already dropped the user from MySQL server.
Resolution:
Revoke all access granted to the user, drop the user, and run FLUSH PRIVILEGE command to remove the caches. Now create/drop/alter the user, it will work.
REVOKE ALL ON *.* FROM 'user'@'host';
DROP USER 'user'@'host';
FLUSH PRIVILEGES;
Grant Tables:
The following tables will help you in identifying the user related informations (as of MySQL 5.7):mysql.user: User accounts, global privileges, and other non-privilege columns
mysql.db: Database-level privileges
mysql.tables_priv: Table-level privileges
mysql.columns_priv: Column-level privileges
mysql.procs_priv: Stored procedure and function privileges
mysql.proxies_priv: Proxy-user privilege
mysql.proxies_priv: Proxy-user privilege
Related MySQL Bug Reports:
I hope this post will help you, if you faced this error on some other scenarios or if you know, some other workaround / solution for this error, please add on the comment section. It will be helpful for other readers.