INNER JOIN由UNION ALL在SQL中創建的兩個表格

Question

我想使用UNION ALL命令合併表格。然後我想要INNER JOIN結果與另一個表。我打了以下的結構，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; 

選擇

Answer 2

您需要alias你UNION ALL的結果，從

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