SQL Server 2012中的列名稱錯誤

Question

請參閱以下查詢。

select UserStatus,UserStatus from ((Select 'Active' as UserStatus) 
 union (Select 'Inactive' as UserStatus))a order by UserStatus  

錯誤：

Msg 209, Level 16, State 1, Line 3
Ambiguous column name 'UserStatus'

解：

ALTER DATABASE VCarePortal
SET COMPATIBILITY_LEVEL = 100

90 = SQL Server 2005`enter code here`
100 = SQL Server 2008 and SQL Server 2008 R2
110 = SQL Server 2012.

我嘗試了有關兼容性級別模式。 但仍然我得到模棱兩可的錯誤。

Answer 1

請刪除一個UserStatus並嘗試：

select UserStatus from 
(
    (Select 'Active' as UserStatus) 
    union 
    (Select 'Inactive' as UserStatus)
)a order by UserStatus

Answer 2

您選擇同一列兩次，然后刪除其中一列，從而解決了該問題。 無論如何，您都不需要兩次，因為聯合的每個選擇僅返回一列。

select UserStatus from ((Select 'Active' as UserStatus) 
 union (Select 'Inactive' as UserStatus))a order by UserStatus 

Answer 3

在訂購同一列時，這里會產生歧義，因此sql引擎無法理解需要訂購哪一列。

因此，使用以下查詢將解決您的問題。

-- Order by 1 means order with first column in selection
select UserStatus, UserStatus 
from (
(Select 'Active' as UserStatus) 
 union 
 (Select 'Inactive' as UserStatus)
)a order by 1 


-- Or remove duplicate column from selection.
select UserStatus
from (
(Select 'Active' as UserStatus) 
 union 
 (Select 'Inactive' as UserStatus)
)a order by UserStatus