Compare the numbers of orders between the Eastern and Western stores in 2015.
in 2015 refers to strftime('%Y', "Order Date") = '2015'; Eastern store refers to east_superstore; Western store refers west_superstore;
SELECT east, west FROM ( SELECT COUNT(`Order ID`) AS east , ( SELECT COUNT(`Order ID`) FROM west_superstore WHERE `Order Date` LIKE '2015%' ) AS west FROM east_superstore WHERE `Order Date` LIKE '2015%' )