List the brands of root beer produced by Dr Pepper Snapple Group and calculate their percentage of purchases between 2014 to 2016.
brand of root beer refers to BrandName; produced by Dr Pepper Snapple Group refers to BreweryName = 'Dr Pepper Snapple Group'; percentage of purchases = MULTIPLY(DIVIDE(SUM(BrandID WHERE PurchaseDate > = '2014-01-01' AND PurchaseDate < = '2016-12-31'), COUNT(BrandID) WHERE BreweryName = 'Dr Pepper Snapple Group'), 1.0); between 2014 to 2016 refers to PurchaseDate > = '2014-01-01' AND PurchaseDate < = '2016-12-31;
SELECT T1.BrandName , CAST(SUM(CASE WHEN T2.PurchaseDate >= '2014-01-01' AND T2.PurchaseDate <= '2016-12-31' THEN 1 ELSE 0 END) AS REAL) / COUNT(T2.BrandID) AS purchase FROM rootbeerbrand AS T1 INNER JOIN rootbeer AS T2 ON T1.BrandID = T2.BrandID WHERE T1.BreweryName = 'Dr Pepper Snapple Group' GROUP BY T2.BrandID