sql中多表的数据统计?
表1:date bh sl memo
04/03/01 01 20 in
04/03/01 02 30 in
04/03/02 01 10 in
04/03/02 02 20 in
表2:date bh sl memo
04/03/01 01 20 out
04/03/01 02 30 out
04/03/02 01 10 out
04/03/02 02 20 out
bh为编号,sl为数量。
现要统计每个编号的表1数量之和,表2数量之和即为:
01 sum(表1.sl) sum(表2.sl)
02 sum(表1.sl) sum(表2.sl)
如何写sql.