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分享SQL语句怎么写呀？
有A、B、C三个表。
A有：a1,a2字段
B有:a1,b1字段
C有：a1,c1字段
select (a2-b1-c1) as 余额 from A,B,C where A.a1=B.a1 and A.a1=C.a1
我想实现当B或C中没有a1,而A表中a1肯定都有的时如:
select (a2-b1) as 余额
select (a2-c1) as 余额
select a2 as 余额
一条SQL语句怎么写呀？
急用，谢谢了！
A有：a1,a2字段
B有:a1,b1字段
C有：a1,c1字段
select (a2-b1-c1) as 余额 from A,B,C where A.a1=B.a1 and A.a1=C.a1
我想实现当B或C中没有a1,而A表中a1肯定都有的时如:
select (a2-b1) as 余额
select (a2-c1) as 余额
select a2 as 余额
一条SQL语句怎么写呀？
急用，谢谢了！
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softrookie 2002-12-19
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where c.a1 not in (select a.a1 from a,b where a.a1=b.a1)
where b.a1 not in (select a.a1 from a,c where a.a1=c.a1)
from a where (a1 not in (select a1 from b)) and (a1 not in (select a1 from c))
where c.a1 not in (select a.a1 from a,b where a.a1=b.a1)
where b.a1 not in (select a.a1 from a,c where a.a1=c.a1)
from a where (a1 not in (select a1 from b)) and (a1 not in (select a1 from c))
