[AccessD] Nz trap with dates in queries

That issue has been around forever, Gustav.  Nz always needs to be cast
into a datatype unless you're looking for a string.

Charlotte

On Thu, May 2, 2013 at 12:08 AM, Gustav Brock <gustav at cactus.dk> wrote:

> Hi all
>
> I browsed this article:
>
> http://www.fmsinc.com/MicrosoftAccess/query/sort/multiple-dates.htm
>
> and much to my surprise the note about the Nz trap is true.
>
> When used in a query, this expression returns a string:
>
>     DateNotNull: Nz([DateFieldWithNulls], Date())
>
> You can easily see it, because if you apply a date format to the column, it
> has no effect.
>
> The real strange part, however, is that if you add two other columns:
>
>     TypeDate: VarType([DateFieldWithNulls])
>     TypeDatez: VarType(Nz([DateFieldWithNulls], Date()))
>
> the first returns 7 (DateTime) and 1 (Null) while the other returns 7s only
> ... no 8s for string!
>
> The workaround is either of these methods - the first corrects the result,
> the second (from the article) uses a good, old alternative:
>
>     DateNotNull: CDate(Nz([DateFieldWithNulls], Date()))
>     DateNotNull: IIf([DateFieldWithNulls] Is Null, Date(),
> [DateFieldWithNulls])
>
> /gustav
>
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