Check if user exists help

Dave_Stro

I am creating a registation form on my website and I dont want multiple users to have the same user name. I am having problems checking if the user already exists in the MySQL db.

This is what I have.

// Verify if user name already exisits
$ucount = mysql_result(mysql_query("SELECT COUNT(*) AS ucount FROM members WHERE username = '{$_POST['username']}' "), 0");

// If username exists display error
if($ucount > 0)
{
$error = true;
$errors .= $_POST['username']." already exists, Please choose another.\n\n";
}

Can anyone tell where I went wrong or show me a better way to check if user exists.

Thank you,
Dave

SuperCam

Whoa man, I don't think I've ever seen a result like this. Here is how I'd do it:

/// I dunno what the whole "COUNT(*) AS ucount" is...
$result = mysql_query("SELECT COUNT(*) AS ucount FROM members WHERE username = '$_POST['username']' ");
$ucount = mysql_num_rows($result);

// If username exists display error 
if($ucount > 0) 
{ 
$error = true; 
$errors .= $_POST['username']." already exists, Please choose another.\n\n"; 
}

Either way, this should help you, because what you have to do is use mysql_num_rows to see how many rows it returned, if it returns more then 0 then that user exists.

laserlight

I would use something along the lines of:

//set $username to the safe (e.g. escaped) version of $_POST['username']
$query = mysql_query("SELECT username FROM members WHERE username='$username'");
if (mysql_num_rows($query) > 0)
{
	//username taken
}

Dave_Stro

lol...I need to smack myself in the head. I forgot to use the mysql_num_rows.

Oh and using the "mysql_result" the way I did. I have read up a little more and found out this is not the best way to do things. I am fairly new to programming, but getting a pretty good grasp of it now.

I had picked up that style from php freaks. Tried it out on a few things and it seemed to work pretty well. I then read in the php manual it cause's poor performance on larger db query's. So not going to use that anymore.

Thanks for the help.

ahundiak

Really nothing wrong with using count in some cases. It's just another tool.

If you really want to prevent duplicate user names then create a unique index on user name. Then just check to see if your insert fails. Relying on a pre check is not a real good design as duplicate names can slip in between the cracks.

Dave_Stro

Thanks laserlight I like the shorter code and it does make it easier to read. This will also work well once making setting the username to unique. Thanks ahundiak for pointing that out to me.