Duplicate entry '' for key 2 - please help!!

[bian101]

Hey guys!

 

I know, I know this problem is EVERYWHERE but i just dont understand! I have a solid knowlage of php but my SQL skills are low, so i dont know too much about Keys and stuff. But my error is: Duplicate entry '' for key 2.

 

The thing that im working on at this section is logging in with facebook. The code that presents my error is:

 

    $sql = "SELECT * FROM users WHERE uid=".$uid;
    $fbid = mysql_query($sql);	
$num_rows = mysql_num_rows($fbid);

if(mysql_num_rows($fbid) < 1) {
	echo "You are not logged in.    ";
	mysql_query("INSERT INTO `users` (`uid`) VALUES ('".$uid."')")
	or die(mysql_error());  

	} else {
	mysql_query("UPDATE users SET logged = '1' WHERE uid=".$uid);
	//mysql_query("UPDATE users SET full_name = $me WHERE uid=".$uid);

	echo "Your Logged in ";
	echo $me['name'];
	?> Continue to <a href="removed "> My Settings </a>. <?			
}

 

Any help is welcome

[bian101]

Any one know much on this topic?

[Pikachu2000]

You're attempting to insert a duplicate value into a table field that is a unique indexed field. Just like the error says. A login script shouldn't need an INSERT query at all (in general).

[sasa]

try to change

$sql = "SELECT * FROM users WHERE uid=".$uid;

with

$sql = "SELECT * FROM users WHERE uid='".$uid."'";

[bian101]

Hey,

 

Somehow i dont know why without me changing that its been implemented, not a clue how i managed to change it, but still no fix. We think its something to do with a key in the database? Not a clue

[Zane]

What's the datatype for the primary key?

 

And also, is it set to auto-increment?