SELECT 
  prices.product_id, 
  prices.lower_limit, 
  usergroup_id, 
  prices.percentage_discount, 
  IF(
    prices.percentage_discount = 0, 
    prices.price, 
    prices.price - (
      prices.price * prices.percentage_discount
    )/ 100
  ) as price 
FROM 
  cscart_product_prices prices 
WHERE 
  prices.product_id = 1127 
  AND lower_limit > 1 
  AND prices.usergroup_id IN (0, 0, 1) 
ORDER BY 
  lower_limit