Checking if username is taken.

Anon

I want to make a script that will allow a user to register for an account on my web site. I know I am going to use a mySQL table to stor all of the users information. i.e. Username, encrypted password, e-mnail, ect. The part that has me confused is how i would go about checking to see if a username already exsists in the user table. Any help is appreciated! Thank you.

toma42

er, this is so simple that you may have a very hard time with the rest of your site if you're running into problems so soon.

Do a select from the user table and if you find rows for the new id you are checking, it's a duplicate.

Anon

Simple it is. I have made other scripts (2) that use a database. I just wasn't thinking. Thanks for the help any way.

Anon

Another (possibly more efficient) option is to make the username field unique (primary key) in the table. Do an insert of the username and check the error code returned. If the name is already taken, you get a 'no duplicates allowed" error and you let the user know. If the insert is successful, you keep on chugging. That way you don't have to do two SQL statements, a select and then an insert--just the insert.

kparker

Your solution is better, but it's for a more important reason that mere efficiency. More importantly, the query-first method leaves a small time window when 2 or more users could be looking for the same user ID, and depending on the time-slicing in the webserver and dbms more than 1 of them could discover that the name was unused, and thus proceed to try to use it. Your method completely eliminates this race condition.