I currently have a set of drop down parameters that pass dates to a query. There is a display value available to select for each Work Week. 

Create Date Parameter:

> 
> 
> > 
> > Display in the drop down: 2016 01 (1/3/2016) P01-16 Q1-16
> > 
> > 
> > Value being passed to the SQL is WEEK\_BEGIN\_DATE: 1/3/2016
> > 
> > 
> > 
> 
> 
> 

New Ship Date Parameter:

> 
> 
> > 
> > Display in the drop down: 2016 01 (12/27/2016) P12-15 Q4-15
> > 
> > 
> > Value being passed to the SQL is SHIP\_WEEK\_BEGIN\_DATE: 12/27/2016
> > 
> > 
> > 
> 
> 
> 

I would like to be able to make both of these optional. 

I tried the following in the parameter value SQL to get the parameter to allow nulls but I got a data type error. I did start going down the cast as varchar() route but it was getting messy quick.

```
SELECT 'NULL' AS WEEK_BEGIN_DATE
UNION
SELECT d.WEEK_BEGIN_DATE FROM DATE d

```

Any suggestions are much appreciated. Let me know if I can provide any other helpful info.