How to divide two values from a data table ensuring that it is not divided by zero?

[BaseballGraphs]

Hello,

I am trying to divide one value from my data table with an associated ID by another value from my data table with a different ID for the same day that the value was added to the data table.

I update my data table daily with several values that have different IDs that label the value type.

Certain of the values I add to my data table also have a value of 0. Therefore, if I want to divide one value by another, I have to ensure that the rows that contain a value of 0 are not counted.

After I divide all of the values into a new value, I then need to store that value in my data table with a new ID so that I can differentiate it.

I have some code that I've been working on but am getting tricked up at this point and would appreciate any further assistance.

<?

  function getValue ( $iPlayer, $iStat ) {
    $sql = sprintf( "SELECT value FROM data WHERE player_id = '%d' and statistic_id = '%d' and day = CURdate()", $iPlayer, $iStat);
	$result = mysql_query ( $sql );
  }

  function getListofPlayers ( ) {
    $sql = 'SELECT player_id FROM data WHERE day = CURdate()';
	$result = mysql_query ( $sql );
  }

  function storeValue ( $iPlayer, $iStat, $value ) {
    $sql = sprintf( "INSERT INTO data SET player_id = '%d', statistic_id = '%d', value = '%s', day = NOW()", $iPlayer,  $iStat,  $value );
	$result = mysql_query ( $sql );
  }

  $aPlayer = getListOfPlayers();
  foreach ( $aPlayer as $oPlayer ) {

   $stat_id_1 = 9;
   $stat_id_2 = 4;
   $stat_id_new = 39;

    $a = getValue( $oPlayer->id, $stat_id_1 );
    $b = getValue( $oPlayer->id, $stat_id_2 );
    $c = $a / $b;

   storeValue ( $oPlayer->id, $stat_id_new, $c );

  }

?>

[Markus]

Check if the value is 0?

if variable equals 0
  do not divide
else
  do divide
endif