What percentage of customers who paid with a Discover Credit Card gave a 3-star rating?
percentage = MULTIPLY(DIVIDE(COUNT(CustomerID WHERE StarRating = 3), COUNT(CustomerID) WHERE CreditCardType = 'Discover'), 100); Discover Credit Card refers to CreditCardType = 'Discover'; 3-star rating refers to StarRating = 3;
SELECT CAST(COUNT(CASE WHEN T1.StarRating = 3 THEN 1 ELSE NULL END) AS REAL) * 100 / COUNT(T1.CustomerID) FROM rootbeerreview AS T1 INNER JOIN `transaction` AS T2 ON T1.CustomerID = T2.CustomerID WHERE T2.CreditCardType = 'Discover'