问题详情
求每个交易所的平均单价的SQL语句是
A)SELECT交易所,avg(单价)FROM stock GRDER BY单价
B)SELECT交易所,avg(单价)FROM stock ORDER BY单价
C)SELECT交易所,avg(单价)FROM stock ORDER BY交易所
D)SELECT交易所,avg(单价)FROM stock GROUP BY交易所