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phpmysqldatabaseregistration

Check if username already exists in database MySQL PHP

I have a registration.php page I made and I need to check if a username is already in my database so that I won't have 2 members with the same name...

Here is how I am inserting the user info into the database (username, password, date of registration, etc.):

mysql_query("INSERT INTO UserDb (ID, TimeStamp, UserName, Password) VALUES ('$ipaddress', NOW(), '$user_username', '$user_password')");

How can I check that database "UserDb" under the "UserName" field to make sure the user's variable "$user_username" doesn't already exist?

Solution

  • You can make the username field in the database a primary key or unique, which guarantees the username uniqueness in the database.

    Then, if you try to insert an already existing username the mysql_query() function will fail, returning FALSE.

    Besides that, you should always query the database for the existence of the username, using a simple select statement:

    SELECT username FROM table WHERE username='$php_username_var';