使用传递的变量更新记录

This Update Query seems to work inside MySQL WorkBench but when applying it to my php application doesn't want to work... Both the $TotalSeats & $PerfID parameters have been tested and they output the desired number.

Is this a minor syntax error or am I missing a trick here?

$deductSeats = "UPDATE perf SET Seats=(SELECT SUM(Seats -'$TotalSeats')) WHERE PerfID = '$PerfID'";
            if (mysqli_query($conn,$deductSeats))
            {
                echo 'Query Worked!<br>';
            }
            else
            {
                echo 'Query Didnt Work<br>';
            }





$deductSeats = "deductSeats(`$TotalSeats`,`$PerfID`)";

You can try :

$deductSeats = "UPDATE perf SET `Seats` = `Seats` - ".$TotalSeats." WHERE PerfID = ".$PerfID;

    if (mysqli_query($conn,$deductSeats)) {
        echo 'Query Worked!<br>';
    } else {
        echo 'Query Didnt Work<br>';
    }