Deleting fiscal year stock_mov doesn't delete data's

$sql = "SELECT loc_code, stock_id, SUM(qty) AS qty, SUM(qty*standard_cost) AS std_cost FROM ".TB_PREF."stock_moves WHERE tran_date <= '$to' GROUP by 
        loc_code, stock_id";
    $result = db_query($sql, "Could not retrieve supp trans");
    while ($row = db_fetch($result))
    {
        $sql = "DELETE FROM ".TB_PREF."stock_moves WHERE tran_date <= '$to' AND loc_code = '{$row['loc_code']}' AND stock_id = '{$row['stock_id']}'";
        db_query($sql, "Could not delete stock moves");
        $qty = $row['qty'];
        $std_cost = ($qty == 0 ? 0 : round2($row['std_cost'] / $qty, user_price_dec()));
        $sql = "INSERT INTO ".TB_PREF."stock_moves (stock_id, loc_code, tran_date, reference, qty, standard_cost) VALUES
            ('{$row['stock_id']}', '{$row['loc_code']}', '$to', '$ref', $qty, $std_cost)";   
        db_query($sql, "Could not insert stock move");
    }