Question

我想在cte中使用这个代码的用例：

Declare @DefinitionType Int = 1
;With Res
As
(
    Case @DefinitionType
        When 1 Then (Select [ActionId], [Title] From Actions)
        When 2 Then (Select [AreaId], [Title] From Areas)
        Else (Select [ContractorScopeId], [Title] From ContractorScopes)
    End
)
Select * From Res

该错误是：

Msg 156，Level 15，State 1，Line 5
关键字“Case”附近的语法不正确。

如何在CTE中使用Case satement？

Answer 1

你不能。

如果列具有兼容的数据类型，则可以执行

DECLARE @DefinitionType INT = 1;

WITH Res
     AS (SELECT [ActionId],
                [Title]
         FROM   Actions
         WHERE  @DefinitionType = 1
         UNION ALL
         SELECT [AreaId],
                [Title]
         FROM   Areas
         WHERE  @DefinitionType = 2
         UNION ALL
         SELECT [ContractorScopeId],
                [Title]
         FROM   ContractorScopes
         WHERE  @DefinitionType = 3)
SELECT *
FROM   Res

如何在CTE sql中使用Case语句？

1 个答案: