Question

Working on a script in Microsoft VBA to take a massive flat database and split it between about 20 different tables. The script consists mainly of opening a table, checking every row in the flat database to make sure it’s not a duplicate, then adding the necessary fields. Repeat for every table.

The first time I ran it everything was going well until I tried to process the name O'Malley. I think it’s obvious what went wrong. A quick search on Google turned up this related StackOverflow post. I took their advice and added Replace(str, "'", "''") to every field before inputting it into the new tables. Now I’ve run into a new problem and Google is less helpful.

Replace(null, "'", "''") causes a run-time error, and the flat database is just riddled with null values. I can add an extra line above every Replace() call to check IsNull() and if so put null into the database instead of Replace(str, "'", "''"), although I would prefer a solution that can fit into a single line if possible. Is there any more elegant way to solve this dilemma, or will I need 216 If statements in my code?

EDIT –

Another reason that I’m searching for a more elegant solution is my duplicate checking code. At the moment I have something like the following:

        'Check for duplicates
        'Assume student is duplicate if it shares:
        '   (StudentName and School) or SSN
        Set rstDuplicate = CurrentDb.OpenRecordset("select * from Student where (StudentName = '" & Replace(rstFrom("Student").Value, "'", "''") & "' AND School = '" & Replace(rstFrom("School").Value, "'", "''") & "') OR SSN = '" & Replace(rstFrom("Social").Value, "'", "''") & "'")
        If rstDuplicate.RecordCount = 0 Then
            'Duplicate was not found
            rstTo.AddNew
            ' Add fields to the new table
            rstTo.Update
        End If

Since the Replace() calls are inline with the duplicate checking, if I were to instead use If statements to check for null then I would have to either save the result to a string or update to flat database. A function that returns Replace(str, "'", "''") OR null without the need for extra variables would be ideal.

Answer 1

If you want to keep everything inline, you can use an immediate If function (IIf):

IIf(IsNull(rstFrom("Student").Value), " Is Null", "= " & Replace(rstFrom("Student").Value)

That will be a nightmare to read and maintain, though. You are better off writing your own function to handle the change in comparison operator as well as the apostrophe escaping:

Function CompFld(Val As Variant) As String
    If IsNull(Val) Then
        CompFld = " Is Null "
    Else
        CompFld = "= '" & Replace(Val, "'", "''") & "' "
    End If
End Function

Use it as so:

Dim SQL As String
SQL = "SELECT * FROM Student " & _
      "WHERE (StudentName " & CompFld(rstFrom("Student").Value) & " AND " & _
      "       School " & CompFld(rstFrom("School").Value) & ") " & _
      "   OR (SSN " & CompFld(rstFrom("Social").Value) & ") "
Set rstDuplicate = CurrentDb.OpenRecordset(SQL)
If rstDuplicate.RecordCount = 0 Then
    'Duplicate was not found
    rstTo.AddNew
    ' Add fields to the new table
    rstTo.Update
End If