只要提供思路，sql语句，请高手快 感谢

select BIGTYPE,CARTYPE,STATUS_ID,SALETYPE, sum(qty1) 数量１,sum(qty2) 数量2, sum(qty3) 数量3
from
(
select BIGTYPE,CARTYPE,STATUS_ID,SALETYPE,数量１ qty1,0 qty2,0 qty3
from 表一
union all
select BIGTYPE,CARTYPE,STATUS_ID,SALETYPE,0,数量2,0
from 表二
union all
select BIGTYPE,CARTYPE,STATUS_ID,SALETYPE,0,0,数量3
from 表三
)
group by BIGTYPE,CARTYPE,STATUS_ID,SALETYPE