Question

ALTER PROCEDURE dbo.StoredProcedure8
@emp_code bigint,
@co_id bigint,
@p decimal(8,2) output

AS

SELECT @p = (select sum(tran_value) from emp_ded_ben_trans where emp_code=@emp_code and co_id=@co_id and period_flg=2 and tax_flg=0)

RETURN  

Answer 1

Stored procedures aren’t made to “return values” – that’s what you have stored functions for.

CREATE FUNCTION dbo.CalculateSomething
  (@emp_code bigint, @co_id bigint)
RETURNS DECIMAL(8, 2)
AS BEGIN    
    RETURN
      (SELECT SUM(tran_value) 
       FROM dbo.emp_ded_ben_trans 
       WHERE 
          emp_code = @emp_code AND co_id = @co_id  
          AND period_flg = 2  AND tax_flg = 0)
END

You can then call this stored function like this:

SELECT dbo.CalculateSomething(value_for_emp_code, value_for_co_id)

and get back a DECIMAL(8,2) from the calculation.

Stored procedures will return the number of rows affected by their operation – an INT.

If you need to return a value from a stored proc, you need to use the OUTPUT parameter type and use the technique that AdaTheDev shows – you need to grab the output value into a variable.