Check if randomly generated username is unique [duplicate]

Question

I need to have a system where a random password and username are created for each new user.

As such, I need to make sure the username is unique.

However I cant figure out why the code below isn't working. It isn't a syntax issue. I just can't figure out where I have gone wrong logically.

anyway here is what I have tried:

    $Password= randomPassword();
    $Username = randomPassword();
    $UsernameCheckQuery = mysql_query("SELECT * FROM users WHERE username = '".$Username."'");
    while (mysql_num_rows($UsernameCheckQuery ) >= 1) {
        $Username = randomPassword();
        $UsernameCheckQuery = mysql_query("SELECT * FROM users WHERE username = '".$Username."'");
      }

I know this topic appears elsewhere on Stack Overflow and on the web. However every question I have seen has been using an if statement to check if the username is already used. In my case I cant see how an if statement would work as the randomPassword function could generated two username that already exist in a row.

for one you should probably use a do while loop. php.net/manual/en/control-structures.do.while.php — James McDonnell
– James McDonnell, Commented Nov 21, 2013 at 3:54
@IgnacioVazquez-Abrams I dont think it is. Please see me question about if statements — jamesmstone
– jamesmstone, Commented Nov 21, 2013 at 3:57
It is exactly a duplicate. Don't check if the username already exists, check if the attempt to insert the row failed. — Ignacio Vazquez-Abrams
– Ignacio Vazquez-Abrams, Commented Nov 21, 2013 at 4:01
@IgnacioVazquez-Abrams ahh that makes sense - Thanks I believe this question is a duplicate how do i specify that — jamesmstone
– jamesmstone, Commented Nov 21, 2013 at 4:05
I don't thinks it's a dup. OP doesn't want to abort if id exists. He wants to keep trying until success. — 001
– 001, Commented Nov 21, 2013 at 4:11

crafter · Accepted Answer · 2013-11-23 05:23:50Z

1

Try

while (true) {
    $Username = randomPassword();
    $UsernameCheckQuery = mysql_query("SELECT * FROM users WHERE username = '".$Username."'");
    if (mysql_num_rows($UsernameCheckQuery ) < 1) {
       break;
    }
}
echo 'The generated username is '.$Username;

edited Nov 23, 2013 at 5:23

answered Nov 21, 2013 at 5:47

crafter

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1 Comment

jamesmstone Over a year ago

works perfectly just syntax error for break; and logic error <

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