2 lists, copy unique rows

Hi guys,

I am a novice to marco/vba and am hoping to get some guidance on extracing unique values based on two lists(2 sheets).

My scenario:

• Sheet1 has one million lines of serial numbers (master sheet)
• Sheet2 has 200,000 lines with same format. ColumnA=serial
• sheet 2 has some new serials and some existing serials
  
• Serial is 18 digit number saved as text (dunno of that matters)

Solution?

• how can I get vba to check serial agaisnt serial ( Sheet2 ColumnA against Sheet1 column A)
• extract all new serials (unique of sheet 2 only)
• unique lines to export to new sheet or replace sheet2

I am really unsure how to start this... any ideas or pointers?

I've googled my heart out for a week but haven't found anything that works.. I've found formulas& excel functions but they keep crashing my comp because of large data in sheet 1. :(

Thanks in advance for any advice and your time!

can you attach a very small sample file with data and desired result ?

welcome to the forum.

you want to copy cells from Sheet2 to Sheet3 which are not present in Sheet1.

this is a VBA solutioun which uses countif formula to detect nonmatching cells.

i dont know how much time it took to complete the procedure.

because i left the application after seeing in the progress bar that only 15% of the calculations are completed in 10 minutes with 8 processors. :)

i assume A1 contains a header.

Code:

---

Sub copy_nonmatching_cells()

    Dim Rng
    Dim Calc As Long
   
    With Application
        .DisplayAlerts = False
        .ScreenUpdating = False
        .EnableEvents = False
        Calc = .Calculation
        .Calculation = xlCalculationManual
    End With
   
    Set Rng = Worksheets("Sheet2").Range("A2:A" & Cells(Rows.Count, 1).End(xlUp).Row)
   
    With Rng
        .Offset(, 1).Formula = "=CountIf(Sheet1!A2:A1000000,A2)"
        .Calculate
        .Resize(, 2).AutoFilter , Field:=2, Criteria1:="0"
        .Parent.AutoFilter.Range.Columns(1).SpecialCells(xlCellTypeVisible).Copy Sheets("Sheet3").Range("A2")
        .AutoFilter
    End With
   
    With Application
        .EnableEvents = True
        .Calculation = Calc
    End With


End Sub

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