INNER JOIN由UNION ALL在SQL中创建的两个表格

Question

我想使用UNION ALL命令合并表格。然后我想要INNER JOIN结果与另一个表。我打了以下的结构，但它不工作：

(Select * from TableA 
UNION ALL 
Select * from TableB) 
INNER JOIN TableC 
ON somekey 

Answer 1

select * 
    from (Select * from TableA union all Select * from TableB) t1 
    inner join TableC t2 on t1.somekey=t2.somekey; 

选择

Answer 2

您需要alias你UNION ALL的结果，从

SELECT * 
FROM (SELECT * FROM TableA UNION ALL SELECT * FROM TableB) ua 
     INNER JOIN TableC ON TableC.somekey = ua.SomeKey