Need help to optimize the Excel VBA code that aggregates duplicates - excel

Question

Below is my source table
Name Sales
---------------------------------
Thomas 100
Jay 200
Thomas 100
Mathew 50
Output I need is as below
Name Sales
---------------------------------
Thomas 200
Jay 200
Mathew 50
Basically, I have 2 columns that can have duplicates and I need to aggregate the second column based on first column.
Current code I have is as below. Its working perfectly fine. It takes around 45 seconds to run for 4500 records. I was wondering if there is a more efficient way to do this... as it seems to be a trivial requirement.
'Combine duplicate rows and sum values
Dim Rng As Range
Dim LngRow As Long, i As Long
LngLastRow = lRow 'The last row is calculated somewhere above...
'Initializing the first row
i = 1
'Looping until blank cell is encountered in first column
While Not Cells(i, 1).Value = ""
'Initializing range object
Set Rng = Cells(i, 1)
'Looping from last row to specified first row
For LngRow = LngLastRow To (i + 1) Step -1
'Checking whether value in the cell is equal to specified cell
If Cells(LngRow, 1).Value = Rng.Value Then
Rng.Offset(0, 1).Value = Rng.Offset(0, 1).Value + Cells(LngRow, 2).Value
Rows(LngRow).Delete
End If
Next LngRow
i = i + 1
Wend
Note that this is part of a larger excel app and hence I definitely need the solution to be in Excel VBA.

Answer 1

Here you go:
Option Explicit
Sub Consolidate()
Dim arrData As Variant
Dim i As Long
Dim Sales As New Scripting.Dictionary 'You will need the library Microsoft Scripting Runtime
Application.ScreenUpdating = False 'speed up the code since excel won't show you what is happening
'First of all, working on arrays always speeds up a lot the code because you are working on memory
'instead of working with the sheets
With ThisWorkbook.Sheets("YourSheet") 'change this
i = .Cells(.Rows.Count, 1).End(xlUp).Row 'last row on column A
arrData = .Range("A2", .Cells(i, 2)).Value 'here im assuming your row 1 has headers and we are storing the data into an array
End With
'Then we create a dictionary with the data
For i = 1 To UBound(arrData) 'from row 2 to the last on Q1 (the highest)
If Not Sales.Exists(arrData(i, 1)) Then
Sales.Add arrData(i, 1), arrData(i, 2) 'We add the worker(Key) with his sales(Item)
Else
Sales(arrData(i, 1)) = Sales(arrData(i, 1)) + arrData(i, 2) 'if the worker already exists, sum his sales
End If
Next i
'Now you have all the workers just once
'If you want to delete column A and B and just leave the consolidate data:
With ThisWorkbook.Sheets("YourSheet") 'change this
i = .Cells(.Rows.Count, 1).End(xlUp).Row 'last row on column A
.Range("A2:B" & i).ClearContents
.Cells(2, 1).Resize(Sales.Count) = Application.Transpose(Sales.Keys) 'workers
.Cells(2, 2).Resize(Sales.Count) = Application.Transpose(Sales.Items) 'Their sales
End With
Application.ScreenUpdating = True 'return excel to normal
End Sub
To learn everything about dictionaries (and more) check this

Answer 2

With data in cols A and B like:
Running this short macro:
Sub KopyII()
Dim cell As Range, N As Long
Columns("A:A").Copy Range("C1")
ActiveSheet.Range("C:C").RemoveDuplicates Columns:=1, Header:=xlNo
N = Cells(Rows.Count, "C").End(xlUp).Row
Range("B1").Copy Range("D1")
Range("D2:D" & N).Formula = "=SUMPRODUCT(--(A:A= C2),(B:B))"
End Sub
will produce this in cols C and D:
NOTE:
This relies on Excel's builtin RemoveDuplicates feature.
EDIT#1:
As chris neilsen points out, this function should be a bit quicker to evaluate:
Sub KopyIII()
Dim cell As Range, N As Long, A As Range, C As Range
Set A = Range("A:A")
Set C = Range("C:C")
A.Copy C
C.RemoveDuplicates Columns:=1, Header:=xlNo
N = Cells(Rows.Count, "C").End(xlUp).Row
Range("B1").Copy Range("D1") ' the header
Range("D2:D" & N).Formula = "=SUMIFS(B:B,A:A,C2)"
End Sub