Use IN Clause in Store Procedure

Create a user define Function :
Create Function [dbo].[fnSplitter] (@IDs Varchar(100) ) 
Returns @Tbl_IDs Table  (ID Int)  As 

Begin
 -- Append comma

 Set @IDs =  @IDs + ','
 -- Indexes to keep the position of searching

 Declare @Pos1 Int
 Declare @pos2 Int

 -- Start from first character

 Set @Pos1=1
 Set @Pos2=1

 While @Pos1<Len(@IDs)
 Begin
  Set @Pos1 = CharIndex(',',@IDs,@Pos1)
  Insert @Tbl_IDs Select  Cast(Substring(@IDs,@Pos2,@Pos1-@Pos2) As Int)
  -- Go to next non comma character

  Set @Pos2=@Pos1+1
  -- Search from the next charcater

  Set @Pos1 = @Pos1+1
 End
 Return
End


Use this function in SP:
@ID varchar(255)
 
Select * from tablename where ColumnName in(Select ID From fnSplitter(@ID))