how to write a script to look for and correct invalid entries in a table - ms-access

Question

First off I'd like to make perfectly clear that my knowledge of Access and VBA is extremely limited at best. I have an employee database system that due to it's age has been prone to small data corruption issues and controls breaking due to differences between 2003/2007 and 2010. While I've managed to hash out the bulk of the problems, one that has me especially concered is the script we're using to manage access to the database. The system is split between two files, a frontend where users can access the database and a backend file that contains all of the tables.
The issue I have is in the frontend form that handles the logon for the users. The way the access system is set up is the user enters their SSN, then the script finds their SSN in the table and if it exists looks if an access checkbox is checked. If they have access, they're directed to the main menu, if not they get a denied message. What I've found though is for some reason or another, if an entry in the personnel table has an incomplete SSN, the script breaks and anyone can gain access to the database.
There's a query that runs in the frontend that looks at the master personnel table and pulls just the first two columns, SSAN and Access.
The form itself has a visible text box, "Text8", and a hidden Combo Box "Combo4". Combo4 uses the previously mentioned query for the row source (SELECT qryAccess.SSAN FROM qryAccess;), while Text8 is where the user enters their SSN.
Here's the code right now:
Option Compare Database
Private Sub Combo4_AfterUpdate()
' Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
Private Sub Text8_AfterUpdate()
Me![Combo4] = Me![Text8]
' Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
Like I said before, as long as every entry for the SSNs is a full 9-digits, this system works. However, if for some reason the entry is not the full 9 like I just found in my database (and no, I have no idea what caused that to happen, there is an input mask in place, 000-00-0000;;_), this system breaks. You could type in "abc" for the SSN and gain access to the database.
How can I write a small script that pre-checks the table for SSN entries that don't fit the 9-digit format that is set, and if it finds them, resets them to an unused number, such as 000000000, 000000001, etc?
Also, if you have any suggestions on how to streamline the existing code, I'd be more than happy to take them.

Answer 1

Add this function to you application
Public Function IsValidSSN(ByVal SSN As String) As Boolean
'Determines if SSN is a valid social security number
'requires SSN to be in either "#########" or "###-##-####" format
IsValidSSN = (SSN Like "###-##-####") Or _
SSN Like ("#########")
End Function
Also change your function to this:
Private Sub Combo4_AfterUpdate()
' Find the record that matches the control.
If IsValidSSN(Me![Combo4]) Then
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
Else
DoCmd.OpenForm "frmDenied"
End IF
End Sub
Private Sub Text8_AfterUpdate()
Me![Combo4] = Me![Text8]
If IsValidSSN(Me![Text8]) Then
' Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "[SSAN] = '" & Me![Combo4] & "'"
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Me![Access] = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
EDIT
Also why are you using a combobox to enter a SSN? You can use input mask on text box. Also I would highly suggest that you convert your system to some other identification other than SSN because it is easily passable to get past this code to look at the table containing everyones SSN, by holding down shift when opening the application. As for streamlining your code just remove that combobox altogether. If they are typing it into a textbox there is no need to put it into a hidden combobox.

Answer 2

You have a text field, SSAN, and with that input mask the dashes are not included in the stored values. So valid values would be 9 digit strings.
If that is correct, you can use a query to identify any invalid stored values.
SELECT y.SSAN, Len(SSAN) AS LenghtOfSSAN
FROM YourTable AS y
WHERE Len(SSAN)<>9 OR y.SSAN ALike '%[!0-9]%';
That query will return rows where SSAN includes < or > 9 characters, and any values which include characters other than digits.
Note the ALike keyword tells the db engine to expect ANSI wild card characters.  If you prefer Access' * wild card instead, change it to Like '*[!0-9]*'
Once you fix the stored values, add a Validation rule for that SSAN field (Like "#########") to require all values consist of 9 digits.

Answer 3

Since it looks like this became more of a "How do I find the user" than "How do I fix the existing entries", let me throw my hat into the ring.
Unless I completely misunderstand this, the existing (and accepted answer) function is HORRIBLE. You can do this all much more efficiently and with less code. First of all, delete Combo4. No need for it. Then do this:
Private Sub Text8_AfterUpdate()
Dim X as Integer
X = DLookup("Access", "qryAccess", "SSAN = '" & Me!Text8 & "'")
If Nz(X) = True Then
DoCmd.RunMacro "Access"
Else
DoCmd.OpenForm "frmDenied"
End If
End Sub
That's all you need. If the user's SSN was stored incorrectly, he's gonna be denied. 7 digits, 8 digits, doesn't make a difference. Only exact matches get through. That is, assuming 0 = False and 1 = True, which should be the default anyway.