Checking if a username exists

[djdaz]

Hi
I need a way to check a mysql database for a certain username to see if it exists, i tried using both

if(mysql_query("SELECT username FROM ut_users WHERE username='$username'"))

and

if(!mysql_query("SELECT username FROM ut_users WHERE username='$username'"))

The first dosnt check and the second always says that it found a username.

Any other ways to check?

Thanks.

[Weedpacket]

That's because you're getting a result set from mysql_query(). You still need to look inside that to see what the result was.

[selesfan87]

you could:

Run your query
Use the mysql_num_rows() function to see how many rows where returned.
If 0 were returned, safe to register it.
If more than 0 returned, username is already present in the database.

eg:

$query = "SELECT username FROM user WHERE username='$username'";
$result = mysql_query($query,$dbconnectionvar);
$isregistered = mysql_num_rows($result);

if ($isregistered != 0) { echo "Username taken!"; exit; } else {
// insert code and processing
echo "Username registered!"; }

[seby]

something like:

$checkuser = mysql_query("SELECT username FROM ut_users WHERE username='$username'");

if(mysql_num_rows($checkuser) == 0)
{
     echo 'that username is not taken';
}
else
{
     echo 'sorry, that username is taken';
}

[djdaz]

ahh, now i see

Thanks people.

[ahundiak]

And be sure to create an unique index on username and check the error codes when inserting a new one. It's still possible for duplicate usernames to slip past your code in a multi-user enviroment.

In fact, with a unique index you can avoid the initial check all together.