possible help me again to get a percentage of the result also of the total number of bills : 
	
possible help me again to get a percentage of the result also of the total number of bills

this code is calc number of order

SELECT COUNT(*)
FROM (
  SELECT id
  FROM OrderDetails
  WHERE Product IN ('p1','p9')
  GROUP BY id
  HAVING COUNT(DISTINCT Product) = 2) AS t


you can understand me if read it : 

http://stackoverflow.com/questions/35781468/how-to-select-two-products-where-it-is-in-same-orderdetails