Parse CSV, ignoring commas inside string literals in VBA?

Question

I have a VBA application that runs every day. It checks a folder where CSVs are downloaded automatically, and adds their contents to a database. When parsing them, I reali

Answer 1

The first way to solve this problem is to look at the structure of the line from the csv file (int,int,"String literal, will have at most one comma", etc). A naive solution would be (Assuming that the line don't have any semicolons)

Function splitLine1(line As String) As String()

   Dim temp() As String
   'Splits the line in three. The string delimited by " will be at temp(1)
   temp = Split(line, Chr(34)) 'chr(34) = "

   'Replaces the commas in the numeric fields by semicolons
   temp(0) = Replace(temp(0), ",", ";")
   temp(2) = Replace(temp(2), ",", ";")

   'Joins the temp array with quotes and then splits the result using the semicolons
   splitLine1 = Split(Join(temp, Chr(34)), ";")

End Function

This function only solves this particular problem. Another way to do the job is using the regular expression object from VBScript.

Function splitLine2(line As String) As String()

    Dim regex As Object
    Set regex = CreateObject("vbscript.regexp")
    regex.IgnoreCase = True
    regex.Global = True

    'This pattern matches only commas outside quotes
    'Pattern = ",(?=([^"]*"[^"]*")*(?![^"]*"))"
    regex.Pattern = ",(?=([^" & Chr(34) & "]*" & Chr(34) & "[^" & Chr(34) & "]*" & Chr(34) & ")*(?![^" & Chr(34) & "]*" & Chr(34) & "))"

    'regex.replaces will replace the commas outside quotes with semicolons and then the
    'Split function will split the result based on the semicollons
    splitLine2 = Split(regex.Replace(line, ";"), ";")

End Function

This method seems much more cryptic, but does not deppends on the structure of the line

You can read more about regular expressions patterns in VBScript Here

Answer 2

If you are working with MS Access tables, there are advantages in simply importing text from disk. For example:

''If you have a reference to the Windows Script Host Object Model
Dim fs As New FileSystemObject
Dim ts As TextStream

''For late binding
''Dim fs As Object
''Dim ts As Object
''Set fs=CreateObject("Scripting.FileSystemObject")

Set ts = fs.CreateTextFile("z:\docs\import.csv", True)

sData = "1,2,3,""This should,be one part"",5,6,7"

ts.Write sData
ts.Close

''Just for testing, your table will already exist
''sSQL = "Create table Imports (f1 int, f2 int, f3 int, f4 text, " _
''     & "f5 int, f6 int, f7 int)"
''CurrentDb.Execute sSQL

''The fields will be called F1,F2 ... Fn in the text file
sSQL = "INSERT INTO Imports SELECT * FROM " _
     & "[text;fmt=delimited;hdr=no;database=z:\docs\].[import.csv]"
CurrentDb.Execute sSQL

Answer 3

Taking your comments into account you could take the easy way out here

• split on " --> gives you 3 or more entries (could be more due to doublequotes inside the string literal)
• split first part on ,
• keep part 2 to n-1 together (is your string literal)
• split the last part on ,

Answer 4

We had a similar CSV parsing challenge in excel recently, and implemented a solution adapted from Javascript code to parse CSV data:

Function SplitCSV(csvText As String, delimiter As String) As String()

    ' Create a regular expression to parse the CSV values
    Dim RegEx As New RegExp

    ' Create pattern which will match each column in the CSV, wih submatches for each of the groups in the regex
    ' Match Groups:  Delimiter            Quoted fields                  Standard fields
    RegEx.Pattern = "(" + delimiter + "|^)(?:\""([^\""]*(?:\""\""[^\""]*)*)\""|([^\""\""" + delimiter + """]*))"
    RegEx.Global = True
    RegEx.IgnoreCase = True

    ' Create an array to hold all pattern matches (i.e. columns)
    Dim Matches As MatchCollection
    Set Matches = RegEx.Execute(csvText)

    ' Create an array to hold output data
    Dim Output() As String

    ' Create int to track array location when iterating
    Dim i As Integer
    i = 0

    ' Manually add blank if first column is blank, since VBA regex misses this
    If csvText Like ",*" Then
        ReDim Preserve Output(i)
        Output(i) = ""
        i = i + 1
    End If

    ' Iterate over all pattern matches and get values into output array
    Dim Match As Match
    Dim MatchedValue As String
    For Each Match In Matches

        ' Check to see which kind of value we captured (quoted or unquoted)
        If (Len(Match.SubMatches(1)) > 0) Then
            ' We found a quoted value. When we capture this value, unescape any double quotes
            MatchedValue = Replace(Match.SubMatches(1), """""", """")
        Else
            ' We found a non-quoted value
            MatchedValue = Match.SubMatches(2)
        End If

        ' Now that we have our value string, let's add it to the data array
        ReDim Preserve Output(i)
        Output(i) = MatchedValue
        i = i + 1

    Next Match

    ' Return the parsed data
    SplitCSV = Output

End Function

Answer 5

@Gimp said...

The current answers do not contain enough detail.

I'm running into the same problem. Looking for more detail in this answer.

To elaborate on @MRAB's answer:

Function ParseCSV(FileName)
    Dim Regex       'As VBScript_RegExp_55.RegExp
    Dim MatchColl   'As VBScript_RegExp_55.MatchCollection
    Dim Match       'As VBScript_RegExp_55.Match
    Dim FS          'As Scripting.FileSystemObject
    Dim Txt         'As Scripting.TextStream
    Dim CSVLine
    ReDim ToInsert(0)

    Set FS = CreateObject("Scripting.FileSystemObject")
    Set Txt = FS.OpenTextFile(FileName, 1, False, -2)
    Set Regex = CreateObject("VBScript.RegExp")

    Regex.Pattern = """[^""]*""|[^,]*"    '<- MRAB's answer
    Regex.Global = True

    Do While Not Txt.AtEndOfStream
        ReDim ToInsert(0)
        CSVLine = Txt.ReadLine
        For Each Match In Regex.Execute(CSVLine)
            If Match.Length > 0 Then
                ReDim Preserve ToInsert(UBound(ToInsert) + 1)
                ToInsert(UBound(ToInsert) - 1) = Match.Value
            End If
        Next
        InsertArrayIntoDatabase ToInsert
    Loop
    Txt.Close
End Function

You need to customize the InsertArrayIntoDatabase Sub for your own table. Mine has several text fields named f00, f01, etc...

Sub InsertArrayIntoDatabase(a())
    Dim rs As DAO.Recordset
    Dim i, n
    Set rs = CurrentDb().TableDefs("tbl").OpenRecordset()
    rs.AddNew
    For i = LBound(a) To UBound(a)
        n = "f" & Format(i, "00") 'fields in table are f00, f01, f02, etc..
        rs.Fields(n) = a(i)
    Next
    rs.Update
End Sub

Note that instead of using CurrentDb() in InsertArrayIntoDatabase(), you should really use a global variable that gets set to the value of CurrentDb() before ParseCSV() runs, because running CurrentDb() in a loop is very slow, especially on a very large file.

Answer 6

A simple regex for parsing a CSV line, assuming no quotes inside quoted fields, is:

"[^"]*"|[^,]*

Each match will return a field.