SQL Statement as Parameter for Stored Proc

Question

This works fine in SQL script, but doesn't work when converting the script to a sp.  It doesn't like how I've defined the @PeriodEndDate parameter.  How do I set the variable to the results of a SQL statement?
CREATE PROCEDURE usp_ARAging 
-- Add the parameters for the stored procedure here
@FiscalYear int = 2014, 
@FiscalPeriod int = 5,
@PeriodEndDate date = (SELECT MAX(JEDate) FROM ERPSQL01.EpicorNamg905.Accounting.Dim_JEDate
WHERE FiscalYear = @FiscalYear
AND FiscalMonth = @FiscalPeriod)
Kirk P.

Answer 1

Let's start over.  The default value of a procedure argument is a "suggestion" - a value to be used when it is not provided by the caller.  So is your goal to allow the user to supply any date, not just the one that coincides with the
fiscal year and period values?  IF not, then it should not be a parameter and the value should be determined by the code inside the stored procedure. 
However, if your goal is to allow any value, then you must follow the rules for specifying an appropriate default and those rules are very restrictive.  You cannot use a query nor can you refer to other parameters.  The typical approach is to use
a "marker" value which the caller uses to indicate that it wants to use the true "default" value which you would then determine inside your stored procedure.  Often a value of NULL is used; in your procedure the code checks this parameter
for a null value and, if found, assigns it the value you used in your query above.
And while we're at it, you should code defensively and check that the set of values supplied as parameters are consistent with each other and with the logic that depends on them.  For example, presumably the period argument should be between 1 and 12
(and not null).  I suggest you reconsider the use of integers since the domain of these values FAR EXCEEDS that allowed for years and months for most business purposes.