Return String with Stored Procedure - string

Question

I have another post with more detailed code, but I think that my problem lies in the following logic. Is it possible to have a stored procedure, call another stored procedure, and the called procedure return a string to be used in the first stored procedure?
Example:
ALTER PROCEDURE [dbo].[SP1]
-- Add the parameters for the stored procedure here
#output nvarchar(30)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
Declare #SP2Input nvarchar(30) = 'Input';
Declare #SP2Output nvarchar(30);
Execute #SP2Output = SP2 #SP2Input, #SP2Output;
If #SP2Output = 'Success'
Begin
Set #output = 'This worked';
End
Else
Begin
Set #output = 'This did not work';
End
Select #output;
END
Here is the next stored procedure:
ALTER PROCEDURE [dbo].[SP2]
-- Add the parameters for the stored procedure here
#input nvarchar(30),
#output nvarchar(30) out
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
If #input = 'Input'
Begin
Set #output = 'Success';
End
Else
Begin
Set #output = 'Fail';
End
Select #output;
END
So, what would get returned to whatever calls stored procedure SP1?
Declare #output nvarchar(30);
Execute SP1 #output;
I would assume that 'This worked' would get returned? However, two results are returned:
1) Success
2) This did not work
What am I doing wrong?

Answer 1

There are two ways to get values back from a sub-procedure: OUTPUT parameters and the return value.
OUTPUT parameters are what other languages call reference parameters. If you pass in a #variable its value can be used but also changed within the called procedure. For this to work you need to mark every parameter that you want to be an OUTPUT parameter as such in the definition of the procedure like you did:
ALTER PROCEDURE [dbo].[SP2]
#input nvarchar(30),
#output nvarchar(30) OUT
AS
BEGIN
....
But you also need to mark it as output on every call:
EXECUTE dbo.SP2 #SP2Input, #SP2Output OUT;
Changing the call of dbo.SP2 in you example to this should make it work.
The actual return value of a procedure is always an integer. You specify its value with the return statement in the procedure:
CREATE PROCEDURE dbo.SP3
AS
BEGIN
RETURN 42;
END;
You then can use it this way:
DECLARE #ret INT;
EXEC #ret = dbo.SP3;
PRINT #ret; -- will print 42