Sum of a column's numbers

[Techissue2008]

Hi

I have a column 'profit', I want to show the sum of them.

here is the code:

$totalprofit=0;
$query2 = "SELECT profit FROM client";
$result2 = mysql_query($query2);
while($row = mysql_fetch_array($result2))
	{
		$totalprofit = $profit + $totalprofit;
	}
echo $totalprofit;

The sum of all profit should be positive, but it shows a negative number. What's wrong with $totalprofit = $profit + $totalprofit?

Thanks

[Techissue2008]

If I use SELECT SUM(profit) AS p from client, it returns
#1140 - Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause

I also tried $totalprofit += $profit, still not work

[Techissue2008]

I found out the error:

$totalprofit += $row[0];

Then it is ok.