Excel Highlight Duplicates and Filter by color alternative

Question

My spreadsheet has about 800,000 rows with 30 columns. Customers are interested in duplicate values only in one column. They need the entire row back. For e.g.

Answer 1

Try this Vba-code (and learn a little bit Dutch)

Sub DuplicatesInColumn()
'maakt een lijst met de aangetroffen dubbelingen
Dim LaatsteRij As Long
Dim MatchNr As Long
Dim iRij, iKolom, iTeller, Teller As Long, ControlKolom As Long
iRij = 1

iKolom = 5                   'number of columns in the sheet, Chance if not correct
ControlKolom = 4             'column number where to find the doubles, Chance if not correct

LaatsteRij = Cells(65000, iKolom).End(xlUp).Row: iTeller = iKolom

Sheet1.Activate
For iRij = 1 To LaatsteRij
    If Cells(iRij, ControlKolom) <> "" Then
        MatchNr = WorksheetFunction.Match(Cells(iRij, ControlKolom), Range(Cells(1, ControlKolom), Cells(LaatsteRij, ControlKolom)), 0)
    If iRij <> MatchNr Then
    iTeller = iKolom
    For Teller = 1 To iTeller
      Cells(iRij, iKolom + Teller).Offset(0, 2).Value = Range(Cells(iRij, Teller), Cells(iRij, Teller)).Value
    Next Teller
    End If: End If
Next
End Sub