错误信息：Every derived table must have its own alias？

Question

有A、B、C三个表，我想实现：先把A和B取合集，再将这个合集与C表取交集，也就是实现A∪B∩C，该怎么用SQL语句写呢？
首先感谢liaoxw624的回答，我试了一下
select x1.* from
(
(SELECT id FROM A)
UNION
(SELECT id FROM B)
)x1
INNER JOIN
C AS t1 ON t1.id=x1.id

提示错误信息：Every derived table must have its own alias

于是，我又试了一下这个：
select x2.* from
(
(
(SELECT id FROM A)
UNION
(SELECT id FROM B)
)x1
INNER JOIN
C AS t1 ON t1.id=x1.id
)x2

又提示说最后两行有语法错误，该怎么办呢？

Answer 1

题目太笼统，假设如下1。3个表列结构一样（不一样也可以，但必须保证可以取到相同的列射影）2。三个表都有相同的关键字，假设为ID则SQL文如下select t.* from--A∪B==>t(select * from Aunionselect * from B)t--A∪B∩Cinner join Con t.ID=C.ID