Dcount on multiselect listbox? - ms-access

Question

Me again. This code works fine when only 1 item is selected, however when more than one item is selected I get the error "syntax error (comma) in query expression" on the following line of code:
intCountNull = DCount("*", "Scrubbed", strCriteria & " Is Null")
Here is my code:
Private Sub Command29_Click()
Dim strCriteria As String
Dim intCountNull As Integer
Dim varItem As Variant
'On Error GoTo Err_Command29_Click
Me.Fields_Values.RowSource = ""
For Each varItem In Me!List101.ItemsSelected
strCriteria = strCriteria & "," & Me!List101.ItemData(varItem)
Next varItem
strCriteria = Right(strCriteria, Len(strCriteria) - 1)
intCountNull = DCount("*", "Scrubbed", strCriteria & " Is Null")
Fields_Values.RowSource = intCountNull & " null values found in " & strCriteria
Exit_Command29_Click:
Exit Sub
'Err_Command29_Click:
'MsgBox "Please select a field"
End Sub

Answer 1

... when more than one item is selected I get the error "syntax error (comma) in query expression" on the following line of code: intCountNull = DCount("*", "Scrubbed", strCriteria & " Is Null")
That makes sense. If the list box selections were "field1", "field3", and "field4", your DCount() would throw error #3075, "Syntax error (comma) in query expression 'field1,field3,field4 Is Null'."
The DCount() expression would be evaluated like this SELECT statement:
SELECT Count(*)
FROM Scrubbed
WHERE field1,field3,field4 Is Null
And the db engine will definitely complain about that WHERE clause. You can't give it a list of field names and ask it whether the list Is Null. You would have to separately ask whether each field Is Null.
That is the explanation for why you get that error. However, I think you need to change your approach.
Build up the RowSource value list string for Fields_Values as you iterate through List101 selected items. (Make sure you have Value List as the Row Source Type property for Fields_Values.) Here is a tested sample which does what I think you want.
Private Sub Command29_Click()
Dim strCriteria As String
Dim intCountNull As Integer
Dim varItem As Variant
Dim strRowSource As String
Me.Fields_Values.RowSource = ""
For Each varItem In Me!List101.ItemsSelected
strCriteria = "[" & Me!List101.ItemData(varItem) & _
"] Is Null"
intCountNull = DCount("*", "Scrubbed", strCriteria)
'Debug.Print strCriteria, intCountNull '
strRowSource = strRowSource & ";" & intCountNull & _
" null values found in " & _
Me!List101.ItemData(varItem)
Next varItem
'Debug.Print strRowSource '
If Len(strRowSource) > 0 Then
strRowSource = Mid(strRowSource, 2)
Me.Fields_Values.RowSource = strRowSource
End If
'Debug.Print strRowSource '
End Sub
Also I don't see why the user should even be allowed to click Command29 unless List101 contains selected items. So consider disabling Command29 until selections have been made.
Private Sub Form_Load()
Me.Command29.Enabled = False
End Sub
Private Sub List101_AfterUpdate()
Me.Command29.Enabled = (Me.List101.ItemsSelected.Count > 0)
End Sub
Finally, I'll suggest you do yourself a favor by giving your controls meaningful names ... Command29 could be cmdShowNullCounts and List101 could be lstFieldNames. Meaningful names are especially helpful when you're dealing with dozens of controls. You should also find them helpful when you need to revisit the form design after a few months. Anyone else who has to take over in the future will appreciate your courtesy.