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