MS Access DLookUp malfunction - vba

Question

I have a very weird problem occurring in MS Access which I can't seem to figure out.
Summary: I have a table from Sharepoint that is connected to my MS Access database and a Person table in my Ms Access db. I pull the information row by row from the Sharepoint table and add it to Person Table.
However, before adding the new data I must check if that specific Person already exists in my table. I check for 'Lastname', 'Firstname' and 'Date created' using DLookup function.
Here where everything goes side ways. DLookup returns me a NULL for almost half of the records that already exist in Person Table. After playing a lot with the condition in DLookup statement my conclusion is that there is a problem with the 'Date created' parameter, yet I have tried using "#" and CDate and even Format, nothing works.
I can't share the data, since it's sensitive, however the syntax for DLookup I'm using is the following:
sqlStr = "LastName=" & Chr(34) & rs![Last Name] & Chr(34)
& " AND FirstName=" & Chr(34) & rs![First Name] & Chr(34)
& " AND DateLastModified=" & Format(dateVar, "dd/mm/yyyy")
DLookup("LastName", "table_Person", sqlStr)
P.S: I have tried DCount, same thing happens. DCount returns 0 yet I know for a fact the record is there.

Answer 1

To build criterias BuildCriteria is your Friend.
Sub TestBuildCriteria()
Dim strCriteria As String
strCriteria = BuildCriteria("OrderDate", dbDate, [Date created])
MsgBox strCriteria
End Sub
Sub YourCode()
sqlStr = BuildCriteria("LastName", dbText, "=" & rs![Last Name]) & _
" AND " & BuildCriteria("FirstName", dbText, "=" & rs![First Name]) & _
" AND " & BuildCriteria("DateLastModified", dbDate, "=" & dateVar)
End Sub
This echoes the proper formated date. Also useful for other data-type. E.g. it escapes Quotation Marks in Strings. Read Custom Filters using BuildCriteria() too.
But there is a far easier alternative.
Create a unique composite index on LastName, FirstName and DateLastModified in the the table. Now you can't insert a duplicate as it has to be unique. If you try you will receive an error msg. Be aware of transaction rollbacks (e.g. Multiple inserts, one fails by key violation -> all actions will be reverted due transaction rollback if you use db.Execute SQL, dbFailOnError).

Answer 2

To check for dates use:
"DateLastModified=#" & FormatDateTime(dateVar, vbShortDate) & "#"
if dateVar can be null you need something like this:
FormatDateTime(Nz(dateVar,CDate("1/1/2000")), vbShortDate)
And of course that just checks the date part. If your dateVar can also have a time part then you have to use
DateValue(dateVar)

Answer 3

Your syntax is not correct. You should put square brackets around field names as is pointed out in documented examples at MSDN
sqlStr = "[LastName]=" & Chr(34) & rs![Last Name] & Chr(34)
& " AND [FirstName]=" & Chr(34) & rs![First Name] & Chr(34)
& " AND [DateLastModified]=#" & Format(dateVar, "dd/mm/yyyy") & "#"
DLookup("[LastName]", "table_Person", sqlStr)

Answer 4

In this situation, my advice would be to simplify the criteria part of the DLOOKUP/DCOUNT until you get something that works, and only then start to make the criteria more complex. I call this 'sanity checking'.
Date/Time criteria often cause problems, so first check that you can make it work without the Date part of the criteria.
For example, in your case, check that this works.
Use the Debug Window (Ctril+G) to test this:
? DCount("*", "table_Person", "LastName=" & Chr(34) & rs![Last Name] & Chr(34))
Then try:
? DCount("*", "table_Person", "LastName=" & Chr(34) & rs![Last Name] & Chr(34) & " AND FirstName=" & Chr(34) & rs![First Name] & Chr(34))
Once you have that working, add in the Date criteria.
Building the criteria up in stages like this, allows you to confirm which part is actually causing the problem.
I'm in the UK, and so I have my dates displayed in UK format - 'DD/MM/YYYY'.
However, when specifying a date criteria for a DLOOKUP/DCOUNT, I always have to format the date to US format. I've often used a simple function to swap the digits into the correct order for the criteria:
Function HashDate(dD As Date) As String
HashDate = "#" & Format$(dD, "MM/DD/YYYY") & "#"
End Function
In the the Debug Window:
? Date
09/03/2018
? HashDate(Date)
#03/09/2018#