SELECT 
  cscart_product_prices.product_id, 
  MIN(
    IF(
      cscart_product_prices.percentage_discount = 0, 
      cscart_product_prices.price, 
      cscart_product_prices.price - (
        cscart_product_prices.price * cscart_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_product_prices 
WHERE 
  cscart_product_prices.product_id IN (
    42270, 42269, 42268, 42267, 42266, 42265, 
    42264, 42263, 42262, 42261, 42260, 
    42259, 42258, 42257, 42256, 42255, 
    42254, 42253, 42252, 42251, 42250, 
    42249, 42248, 42247, 42246
  ) 
  AND cscart_product_prices.lower_limit = 1 
  AND cscart_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_product_prices.product_id