I want to use following Statement

```
DECLARE @MatnrFilter TABLE ( ListValue VARCHAR(50) )

INSERT  INTO @MatnrFilter
    ( ListValue )
VALUES  ( '167436' )
INSERT  INTO @MatnrFilter
        ( ListValue )
VALUES  ( '167447' )

SELECT  *
FROM    ios.BaseData_2013
WHERE   Materialnummer IN ( CASE WHEN ( ( SELECT TOP 1
                                                ListValue
                                      FROM      @MatnrFilter
                                    ) IS NULL ) THEN Materialnummer
                             ELSE ( SELECT  *
                                    FROM    @MatnrFilter
                                  )
                        END ) 

```

I want to filter just when there are values in @MtnrFilter. Here I am getting the error message 

```
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

```

Is there another way to do that?

Tanks 
Andi