Use Stored Procedure Output Parameters in SSRS

It’s commonly known that there are a few frustrations when using stored procedures as the source for SSRS 2005 datasets, the inability to cope with temporary tables is always a key one, another is not being able to get at output parameters or return values.

This post explains the easiest way to get at the output parameters and return value.

Lets assume you are using the following stored proc:

IF OBJECT_ID('myProc') IS NOT NULL
  DROP PROCEDURE myProc
GO
CREATE PROCEDURE dbo.myProc
  @OutTest int OUTPUT
AS
  SET @OutTest = 42

  --Random test query
  SELECT 1 as x, 'rec1' as y, 'rec1' as z
  UNION
  SELECT 2, 'rec2', 'rec2'

  RETURN 1
GO

When we set the dataset to use myProc, we will get the three fields (x, y and z) returned, but not the @OutTest parameter, or the return value of 1.

To fix this all you need to do is create a wrapper procedure that converts the values into extra fields.

IF OBJECT_ID('myProcWrapper') IS NOT NULL
  DROP PROCEDURE myProcWrapper
GO
CREATE PROCEDURE dbo.myProcWrapper
AS

  CREATE TABLE #myTmp(
    x int,
    y varchar(20),
    z varchar(20)
  )

  DECLARE @ReturnValue int, @OutTest int

  INSERT INTO #myTmp
    EXEC @ReturnValue=dbo.myProc @OutTest OUTPUT

  SELECT x, y, z,
      @ReturnValue as RetVal,
      @OutTest as [Output]
    FROM #myTmp

  Drop Table #myTmp

  RETURN 1
GO

This runs the original procedure, and stores the values in a temporary table (yes, I know I know…!). It then appends the return value and output parameters as extra fields and then returns the whole lot. These values are repeated for every record returned, but all you have to do is take the value from the first record =First(Fields!Output.Value).

If you wanted to get rid of the temporary table, you could always replace it with a permenant table, but you’d have to be careful to keep each client instance seperate so results for different users didn’t interfere with each other. You could do this by adding a working column to the myTmp table contaning the username and/or workstation ID. Something like this…

IF OBJECT_ID('myTmp') IS NOT NULL
  DROP TABLE myTmp
GO

CREATE TABLE myTmp(
  x int,
  y varchar(20),
  z varchar(20),
  UserID varchar(50),
  Workstation varchar(50)
)
GO
ALTER TABLE dbo.myTmp ADD CONSTRAINT
  DF_myTmp_UserID DEFAULT SYSTEM_USER FOR UserID
GO
ALTER TABLE dbo.myTmp ADD CONSTRAINT
  DF_myTmp_Workstation DEFAULT Host_Name() FOR Workstation
GO

IF OBJECT_ID('myProcWrapper') IS NOT NULL
  DROP PROCEDURE myProcWrapper
GO
CREATE PROCEDURE dbo.myProcWrapper
AS

  DECLARE @ReturnValue int, @OutTest int

  DELETE FROM myTmp
    WHERE UserID = SYSTEM_USER
    AND Workstation = Host_Name()

  INSERT INTO myTmp (x,y,z)
    EXEC @ReturnValue=dbo.myProc @OutTest OUTPUT

  SELECT x, y, z,
      @ReturnValue as RetVal,
      @OutTest as [Output]
    FROM myTmp
    WHERE UserID = SYSTEM_USER
    AND Workstation = Host_Name()

  DELETE FROM myTmp
    WHERE UserID = SYSTEM_USER
    AND Workstation = Host_Name()

  RETURN 1
GO

This still has the benefit of not having to modify the original stored procedure, but now allows you to see the available fields in Reporting Services.