Why do I get multiple results from a MAX SQL query? - sql

Question

In Access, I have a table named tblBundle and am trying to query the last step that was completed on every bundle in an order.
tblBundle contains: Work Order, Bundle #, BundleLtr, Step, Complete [boolean]
I ultimately want to copy this into vba to create a list of the Bundle #, Ltr, and last step completed for continued data entry on the next step completed.
For some reason I cannot ascertain, the SQL query below returns 2 records for bundle 1 (190, 200) when I believe it should only be returning one record - 200.
SELECT Max(tblBundle.Step) AS intLstep, tblBundle.BundleNbr, tblBundle.BundleLtr,
tblBundle.Complete
FROM tblBundle
GROUP BY tblBundle.WO, tblBundle.BundleNbr, tblBundle.BundleLtr, tblBundle.Complete
HAVING (((tblBundle.WO)="195687-1-1") AND ((tblBundle.Complete)=True));
Can anyone help me figure out why my query is returning the extra value?

Answer 1

In MsAccess, NULL values appear as blanks when viewed on the Datasheet view. Also, it seems that when blanks are entered for a ShortText column on the Datasheet view, they are turned into NULLs (on my version of MsAccess). It seems that your data may have NULL for one of the Steps (say 200), and spaces (zero or more) for the other (say Step 190), you could force your query to treat both the same way:
SELECT Max(tblBundle.Step) AS intLstep, tblBundle.BundleNbr,
nz(tblBundle.BundleLtr,'') as BundleLtr,
tblBundle.Complete
FROM tblBundle
GROUP BY tblBundle.WO, tblBundle.BundleNbr,
nz(tblBundle.BundleLtr,''), tblBundle.Complete
HAVING (((tblBundle.WO)="195687-1-1") AND ((tblBundle.Complete)=True));
Please note that the invisible character can, in fact, be a character that looks like space, but it is not (like non-breaking space), etc. If the above solution does not work, try something like:
SELECT asc(mid(BundleLtr, 1,1)), asc(mid(BundleLtr, 2,1)) FROM Table2 where Step=190
To see the ascii values of the data in that column.

Answer 2

It seems like because your query is breaking down the the result and also returning BundleNbr is causing it to take both Max because its valid.
Also you break this down in your Group By statement and aggregate by that.
Both values of 190 and 200 have a BundleNbr of 1. If you remove that column you'll get the actual max value of 200 (If you want the max of intLStep.

Answer 3

I was able to use this following function to "clean up" my string and remove the additional 'Bundle 1'. This does not solve the original question, but works for my purposes.
'[Removes duplicate values from a string]
Function DeDupeString(ByVal sInput As String, Optional ByVal sDelimiter As
String = ",") As String
Dim varSection As Variant
Dim sTemp As String
For Each varSection In Split(sInput, sDelimiter)
If InStr(1, sDelimiter & sTemp & sDelimiter, sDelimiter & varSection & sDelimiter, vbTextCompare) = 0 Then
sTemp = sTemp & sDelimiter & varSection
End If
Next varSection
DeDupeString = Mid(sTemp, Len(sDelimiter) + 1)
End Function
Found From: Removing Duplicate values from a string in VBA