How many transactions were made in Sac State Union using the American Express credit card in 2014?
Sac State Union refers to LocationName = 'Sac State Union'; American Express credit card refers to CreditCardType = 'American Express'; in 2014 refers to TransactionDate LIKE '2014%';
SELECT COUNT(T1.TransactionID) FROM `transaction` AS T1 INNER JOIN location AS T2 ON T1.LocationID = T2.LocationID WHERE T2.LocationName = 'Sac State Union' AND T1.CreditCardType = 'American Express' AND T1.TransactionDate BETWEEN '2014-01-01' AND '2014-12-31'