oracle双表合并查询
有三张表A、B、C，其中B、C的外键'aid'是A的主键。但是A中的记录不会同时出现在B、C中。现有两条语句：
select b_val from B where aid in (select id from A where ...);
select c_val from C where aid in (select id from A where ...);
请高手指点一下我该怎么把这两句合并成一句，谢谢！！！ Oracle select 合并
[解决办法]
select * from b left join c on b.aid=c.aid where b.aid in (select id from A where ...)
[解决办法]
select b_val
from (select b_val, aid
from B
union all
select c_val, aid from c) t
where t.aid in (select id from A where .. .)
