How many root beers did Tom Hanks purchase between 2015 to 2016?
between 2015 to 2016 refers to TransactionDate > = '2015-01-01' AND TransactionDate < '2016-12-31';
SELECT COUNT(T2.RootBeerID) FROM customers AS T1 INNER JOIN `transaction` AS T2 ON T1.CustomerID = T2.CustomerID WHERE T1.First = 'Tom' AND T1.Last = 'Hanks' AND T2.TransactionDate BETWEEN '2015-01-01' AND '2016-12-31'