php search in database with string

I want to search in a database with variable positions. The variables are created here:

&numbers  //= user input
&naar    // = user input

$number = range($numbers+1, $naar -1); //define the range between the inputs
foreach ($number as $key=>$val){
$number[$key] = $letter.$val;}         //define the array
$string = implode (' ',$number);       // make a string from the array

This works fine. The output is a string that contains a minimum of 0 outputs and a maximun of 7 outputs. For example: A2 A3 A4 A5

I want the database to search if something is at one of the generated positions. Ive got this already:

  $query="select chess_id from stelling where positie=\"".$number."\"";
  $result = mysql_query($query, $connection);
  $spring = 0;
    if(mysql_num_rows($result)>0)                
        {
        $spring = mysql_result($result, 0);
        }
    echo "$spring";

With this code only the last generated $string output will be checked. How can i let the database check all generated string code? For example:

$string = `A2 A3 A4 A5`
$query="select chess_id from stelling where positie=\"".$number."\"";

will only check A5

sample rows from table:

wt,A1 wp,A2 wl,A3 wq,A4