Originally Posted by Dormilich
easiest and most failsafe method is making the username column either the Primary Key or UNIQUE.
Yeah, it's a good solution though. I set it to unique and it doesn't another a same username.
But I need to alert the user that the username is existed. So, the user can register again. How should i do this ? I am searching for the suitable solution for two days. But the codes or guidelines are not working with my codes.