Question

I have an application to add friends. I need to have my script to check, if the users’ already friends. I thought I could do this by a COUNT. I did like this:

            $username = $_GET[user];
            $ven_til_id = $_SESSION['userID'];

            $num = 1;
            if(isset($_GET['add_friend'])){
                $check=("SELECT username,ven_til_id, COUNT(*) AS num FROM friends WHERE username=$username AND ven_til_id=$ven_til_id GROUP BY username,ven_til_id")or die(mysql_error());
                $result=mysql_query($check);
                    if(!$result){
                        echo "Cant run query.";
                    } else {
                        $num = mysql_num_rows($result);
                    }
                    if($num>0){
                        header("Location: /profil/$username?add_error");
                } else {
                $sql=mysql_query("INSERT INTO friends (username,ven_til_id)VALUES('$username', '$ven_til_id')")or die(mysql_error());
                header("Location: /profil/$username");
                }
            }

            ?>

But when I’m adding one friend it’s fine. It adds it and everything is fine. But then when I try to add another, it says we’re already friends. I guess it’s because it’s counting how many times my ID (ven_til_id) is listed in the tables.

Answer 1

You’re missing a comma:

SELECT
 username,ven_til_id COUNT(*) AS num  FROM ...

should be

SELECT
 username,ven_til_id, COUNT(*) AS num  FROM ...

Also, your reference to the count field is incorrect – it should be the third column or $row[2]

You may want to make your code more robust by referring to fields by name eg $row['num']

One final thing to confirm is that the value being retrieved with a count is being treated as an integer not a string. I don’t think it’s the problem here but you may want to explicitly cast it to avoid possible issues later eg…

$num = (int) $row[2];

Option 1
Just select the appropriate rows and see how many records you get back…

SELECT  username,
    ven_til_id
FROM    friends
WHERE   username=$username
AND     ven_til_id=$ven_til_id

Then just count the number of records returned using PHP – eg mysql_num_rows() (I think that’s the correct function name)

Clarification:
Change

                    $row = mysql_fetch_row($result);
                    $num = $row[2];

to

                    $num = mysql_num_rows($result);

Option 2

Get MySQL to do the counting for you – in qhich case you need to tell it to group multiple record together…

SELECT  username,
    ven_til_id,
    COUNT(*) as Num
FROM    friends
WHERE   username=$username
AND     ven_til_id=$ven_til_id
GROUP BY username,
    ven_til_id

Then just read the 3rd value of the first row (num) and you’ll have a count

NB: The second method may be overkill if you’re only ever expecting a 1 or a 0