SELECT Customer.cname , StockTrade.sid , SUM(StockTrade.share) AS '購入總股數' FROM Customer INNER JOIN StockTrade ON Customer.cid = StockTrade.cid WHERE Customer.cname = 'Tom' GROUP BY StockTrade.sid ;
詳解提供者:邊工作邊唸書
SELECT sid,SUM(share) AS 購入總股數 FROM StockTrade WHERE cid=(SELECT cid FROM Customer WHERE cname=‘Tom’) GROUP BY sid;