MySQL Query to find customers who have ordered two specific products

Question

I\'m having trouble coming up with a query that will find all customers who have purchased both PROD1 and PROD2.

Here\'s a pseudo-query that kind of looks like what

Answer 1

(Added new options below using the additional information provided by the user)

Try

SELECT * FROM Customers WHERE 
 EXISTS (SELECT * FROM Purchases WHERE ProductID = 'PROD1' AND CustID = Customers.CustID)
 AND
 EXISTS (SELECT * FROM Purchases WHERE ProductID = 'PROD2' AND CustID = Customers.CustID)

Or

SELECT * FROM Customers WHERE 
 CustID IN (SELECT CustID FROM Purchases WHERE ProductID = 'PROD1')
 AND
 CustID IN (SELECT CustID FROM Purchases WHERE ProductID = 'PROD2')

Or

SELECT UserID FROM Transactions WHERE ProductID = 'PROD1'
 AND EXISTS (SELECT * FROM Transactions WHERE UserID = T1.UserID 
  AND ProductID = 'PROD2')

Or

SELECT UserID FROM Transactions WHERE ProductID = 'PROD1'
 AND UserID IN (SELECT UserID FROM Transactions WHERE ProductID = 'PROD2')