sql如何并表进行查询得出结果

Question

sqlsever如何将表1和表2 并表查询，得出某年某月某日的出库减退货的金额，按照组织分组

Answer 1

select 
sum(case when c.类型='出库' then c.金额 else 0 end) 
-
sum(case when c.类型='退货' then c.金额 else 0 end) 
form (select * from a UNION ALL select * from b) as c group by c.组织,c.年, c.月, c.日