Deleting Duplicate Columns

Dror has a worksheet that contains quite a bit of data. It is possible that the data in one column will be exactly the same as the data in another column, so he wonders if there is an easy way to delete any duplicate columns within the worksheet.

The first step, of course, is to figure out if two columns are identical or not. This can be determined rather easily with an array formula such as the following:

=AND(A1:A100=B1:B100)

(Remember that an array formula is entered by using Shift+Ctrl+Enter.) The formula compares all the values in the first 100 rows of columns A and B. If they are all the same, then the formula returns TRUE. If any of the cells don't match, then the formula returns FALSE. If the result is TRUE you could then delete one of the columns because they are the same.

If you want something that is a bit more automatic, meaning that the duplicate column is deleted, then you'll need to use a macro. The following steps through all the columns in the worksheet and, starting with the right-most column, compares all the columns. If any are the same—regardless of their order in the worksheet—then the macro asks if you want the duplicate column deleted.

Sub DeleteDuplicateColumns()
    Dim rngData As Range
    Dim arr1, arr2
    Dim i As Integer, j As Integer, n As Integer

    On Error Resume Next
    Set rngData = ActiveSheet.UsedRange
    If rngData Is Nothing Then Exit Sub

    n = rngData.Columns.Count

    For i = n To 2 Step -1
        For j = i - 1 To 1 Step -1
            If WorksheetFunction.CountA(rngData.Columns(i)) <> 0 And _
              WorksheetFunction.CountA(rngData.Columns(j)) <> 0 Then
                arr1 = rngData.Columns(i)
                arr2 = rngData.Columns(j)
                If AreEqualArr(arr1, arr2) Then
                    With rngData.Columns(j)
                        'mark column to be deleted
                        .Copy
                        If MsgBox("Delete marked column?", vbYesNo) _
                          = vbYes Then
                            rngData.Columns(j).Delete
                        Else
                            'remove mark
                            Application.CutCopyMode = False
                        End If
                    End With
                End If
            End If
        Next j
    Next i

End Sub

Function AreEqualArr(arr1, arr2) As Boolean
    Dim i As Long, n As Long
    AreEqualArr = False
    For n = LBound(arr1) To UBound(arr1)
        If arr1(n, 1) <> arr2(n, 1) Then
            Exit Function
        End If
    Next n
    AreEqualArr = True
End Function

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (7164) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Deleting Duplicate Columns.