MySQL query using an array

Solution 1:

The second query should use $thelist not $row, and it should be outside of the while loop. The foreach loop is unnecessary when processing a single row. You can access the name in $row with a simple $row[0]. Something like this (untested):

$query1 = "SELECT name FROM clients WHERE sector = '$sectorlink'";
$clientresult = mysql_query($query1, $connection) or trigger_error("SQL", E_USER_ERROR);

while($row = mysql_fetch_array($clientresult)){
    $temp[] = '"'.$row[0].'"';
}

$thelist = implode(",",$temp);
$query = "SELECT count(*) FROM studies WHERE client IN ($thelist) ORDER BY (date) desc";
$result = mysql_query($query, $connection) or trigger_error("SQL", E_USER_ERROR);

Caution: Please be aware that your code is highly vulnerable to SQL injection attacks. It's fine for testing or internal development but if this code is going to be running the Fort Knox web site you're going to want to fix it up quite a bit. Just an FYI. :-)