[AccessD] Nz trap with dates in queries

Is the former, or latter faster?

>>    DateNotNull: CDate(Nz([DateFieldWithNulls], Date()))

>>     DateNotNull: IIf([DateFieldWithNulls] Is Null, Date(),
[DateFieldWithNulls])

Also, wouldn't it be better to assign the Date () to a parameter then use
that parameter in place of Date()? 

Suppose you ran this at 23:59:00 and it is inside a query which takes a long
time to run, wouldn't Date() change for later records?


-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Gustav Brock
Sent: Thursday, May 02, 2013 3:09 AM
To: 'Access Developers discussion and problem solving'
Subject: [AccessD] Nz trap with dates in queries

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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