Question

这种语法有什么问题？

Declare @comparisongroup int;
...
Insert Into @universitytemp Case @comparisongroup
    When -1 Then Select * From dbo.University;
    When -2 Then Select * From dbo.University Where SubDivisionName = @group; 
    When -3 Then Select * From dbo.University Where ConferenceName = @group; 
    Else Select * From dbo.GroupUniversity Where GroupID = CONVERT(int, @group);
End;

这不起作用

Declare @comparisongroup int;
...
Case @comparisongroup
    When -1 Then Insert Into @universitytemp Select * From dbo.University
    When -2 Then Insert Into @universitytemp Select * From dbo.University Where SubDivisionName = @group 
    When -3 Then Insert Into @universitytemp Select * From dbo.University Where ConferenceName = @group 
    Else Insert Into @universitytemp Select * From dbo.GroupUniversity Where GroupID = CONVERT(int, @group)
End;

这两个都没有：

Declare @comparisongroup int;
...
Case
    When @comparisongroup = -1 Then Insert Into @universitytemp Select * From dbo.University;
    When @comparisongroup = -2 Then Insert Into @universitytemp Select * From dbo.University Where SubDivisionName = @group
    When @comparisongroup = -3 Then Insert Into @universitytemp Select * From dbo.University Where ConferenceName = @group 
    Else Insert Into @universitytemp Select * From dbo.GroupUniversity Where GroupID = CONVERT(int, @group)
End;

我收到错误Incorrect syntax near the keyword 'When', 'Else', and 'End'

Answer 1

那是因为CASE是表达式，它返回值。单个值。不是结果集。

您可以尝试：

SELECT
    * --todo - explicit column list
FROM
   dbo.University u
WHERE
   @comparisongroup = -1 OR
   (@comparisongroup = -2 AND SubDivisionName = @Group) OR
   (@comparisongroup = -3 AND ConferenceName = @Group)
UNION ALL
SELECT
    * --todo - explicit column list
FROM
    dbo.GroupUniversity
WHERE GroupID = CONVERT(int, @group) AND NOT @ComparisonGroup in (-1,-2,-3);

即。根本不使用CASE表达式。作为一个风格点，我也可能将@group分成两个参数/变量 - 一个名称中包含“name”，并且继续为（varchar？），另一个是 int，仅用于GroupID比较。

SQL案例语法错误

1 个答案: