Check to see if part number already exists in database

Posted on 2014-11-23
Last Modified: 2014-11-28
I have a form which the user uses to enter a new part in the database.  The following code is supposed to halt the entry if the same part already exists.  Note that PART_NO is a text field.

But the code isn't working, the alert pops up even if the part does not exist already.

    'Code to check for existing part...
    Dim Answer As Variant
    Answer = DLookup("[PART_NO]", "tblParts", "[PART_NO] = '" & Me.txtPART_NO & "'")
    If Not IsNull(Answer) Then
        MsgBox "This part already exists in the database.  Please re-enter the details."
    End If

What am I doing wrong?
Question by:SteveL13
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LVL 120

Expert Comment

by:Rey Obrero (Capricorn1)
ID: 40460662
try this codes instead

     If dcount("*", "tblParts", "[PART_NO] = '" & Me.txtPART_NO & "'")>0  Then
         MsgBox "This part already exists in the database.  Please re-enter the details."
     End If

Author Comment

ID: 40460678
Didn't work.  Sorry.

I am running the code from a command button on a form.  Here is the code with your suggestion in place...

Private Sub cmdCommitPartN_Click()
    'Code to check for existing part...
    If DCount("*", "tblParts", "[PART_NO] = '" & Me.txtPART_NO & "'") > 0 Then
        MsgBox "This part already exists in the database.  Please re-enter the details."
    End If
End Sub

Open in new window

LVL 48

Assisted Solution

by:Dale Fye
Dale Fye earned 250 total points
ID: 40460810
Both your DLOOKUP and Rey's DCOUNT syntax are correct, for what you have described.  You might try:
Dim strCriteria as string

strCriteria = "[PART_NO] = '" & Me.txtPART_NO & "'"
debug.print strCriteria
If dcount("*", "tblParts", strCriteria)>0  Then
    MsgBox "This part already exists in the database.  Please re-enter the details."
End If 

Open in new window

At least this way, you can actually see what is being tested, then you can open tblParts and confirm that the value is actually there.
LVL 51

Accepted Solution

Gustav Brock earned 250 total points
ID: 40460934
You may have better luck using the BeforeUpdate event of the form and its parameter Cancel:

     ' Code to check for existing part...
     Dim Answer As Variant
     Answer = DLookup("[PART_NO]", "tblParts", "[PART_NO] = '" & Me.txtPART_NO & "'")
     Cancel = Not IsNull(Answer)

     If Cancel = True Then
         MsgBox "This part already exists in the database.  Please re-enter the details."
     End If


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