How to find the Maximum Date from Columns

I am trying to pick the correct date (Result Date) when comparing two dates in an Access query.  I am able to determine which date to pick first in an IIf statement if one of the date fields is Null by the following function:

=iif(IsNull(Second Date), First Date)

but I haven't been able to figure out how to add the "then" to pick the Maximum of the remaining dates.  So my data currently looks like (see attachment for clearer view of columns):

First Date                    Second Date        Result Date
3/19/2012                      3/19/2012
10/14/2014      10/14/2014      
8/13/2014      11/24/2014      
3/18/2014                      3/18/2014
6/9/2014                6/9/2014
11/4/2013                      11/4/2013
6/20/2014      12/11/2014      
7/14/2014      11/22/2014      
9/10/2013      12/11/2014      
2/6/2014                2/6/2014
7/25/2012                      7/25/2012

I need guidance on how to get the blanks in the Result Date filled in with the max of the two dates.  Hope this makes sense.  Thanks.
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SimonConnect With a Mentor Commented:
=iif(nz([second date],#1/1/1900#)>nz([first date],#1/1/1900#),nz([second date],null),nz([first date],null))

I haven't got Access in front of me at the moment to test it, but it should give the more recent date of the two, or NULL if both dates are empty.

Or as a column definition in a query...
[Result Date]: IIf(Nz([second date],#01/01/1900#)>Nz([first date],#01/01/1900#),Nz([second date],Null),Nz([first date],Null))
tomfarrarAuthor Commented:
Hi Simon - It is close, but for some reason the second option does not appear to be working.  I am getting the minimum of the Second Date and the First Date.  I need the Max.  Am I looking at this wrong?
When you say Max, I assume you mean the most recent of the two dates?

Are your fields actually dates or text representations of dates?

I just fired up my laptop to test this and I get the correct results (the later date of the two or the only date if one is blank or empty result column if both dates were blank).

Please let me know the actual dates you are using to test this, and possibly  try some extra test cases
e.g. 1/1/2014 v 12/31/2014
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Rey Obrero (Capricorn1)Commented:
try this

ResultDate: IIf([FirstDate]>Nz([SecondDate]),[FirstDate],[SecondDate])
Robert ShermanOwnerCommented:
Alternatively, especially if you need to do this in more than one query, you can put the below code into a module.

This will give you the max of any number of values, and can be put into your query as
ResultDate: max([FirstDate],[SecondDate])

Function max(ParamArray p()) As Variant

    Dim i As Integer
    max = p(0)
    For i = 1 To UBound(p)
        If max < Nz(p(i), "") Then
            max = p(i)
        End If
End Function

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tomfarrarAuthor Commented:
Hi Simon - They are date-defined in the tables.  Here is the actual function, and the result is shown in the attached.  

LAST_USED_DT: IIf(Nz([Transaction_Dates_JDE]![LST_XFER_DT],#1/1/1900#)>Nz([ConversionDateImport Table]![LST_XFER_DT],#1/1/1900#),Nz([Transaction_Dates_JDE]![LST_USED_DT],Null),Nz([ConversionDateImport Table]![LST_USED_DT],Null))
tomfarrarAuthor Commented:
I'd try this

=iif(nz([Second Date],0)>=nz([First Date,0]), [Second Date], First Date)
Nz() is an isnull and iif wrapped together

But what do you want to have happen if both dates are null
These make little sense
Nz([ConversionDateImport Table]![LST_USED_DT],Null)
There's little point in testing for and replacing null just to replace it with null
Rey Obrero (Capricorn1)Connect With a Mentor Commented:

you have four date fields, using the date fields listed below
please explain your requirement

[ConversionDateImport Table]![LST_XFER_DT]
[ConversionDateImport Table]![LST_USED_DT]
tomfarrarAuthor Commented:
Thanks, Rey, that is what happens when I get to the end of the day.  My mistake.  Should always be [LST_USED_DT] for both tables.  Now the functions are working.  I am going home, but will be back to confirm in the morning.  Thanks for everyone chipping in.  Sorry for the error.  - Reilly
tomfarrarAuthor Commented:
A lot of good input; thank you.
tomfarrarAuthor Commented:
Thank, Simon, for the immediate answer as it was important.  Thanks, Rey, for the alternative solution, and pointing out my date error.  I am sure the rest of you have provided good detail that I hope to look at closer as time permits.  Thanks again.  - Reilly
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