Compare two Table(Any efficient way)

[DONE1]

I wrote a code as follows to compare 2 tables on diff worksheet.
Each work sheet has about 6000 Rows.
The code works but appears to Work very slow.
Is there a more efficient way to do it.

Sub MergeTable()
'
''
Dim ROW1 As Long
Dim ROW2 As Long
Dim C1 As String
Dim C2 As String
Dim C3 As String
Dim C4 As String
ROW1 = 2
Do While Sheets("TABLE2").Cells(ROW1, 1).Value <> ""
  ROW2 = 2
  Do While Sheets("TABLE1").Cells(ROW2, 1).Value <> ""
  C1 = Mid(Sheets("TABLE2").Cells(ROW1, 1), 1, 6)
  C2 = Mid(Sheets("TABLE1").Cells(ROW2, 1), 1, 6)

  If ((Sheets("TABLE2").Cells(ROW1, 2).Value = Sheets("TABLE1").Cells(ROW2, 2).Value) And (C1 = C2)) Then
  
   Sheets("TABLE2").Cells(ROW1, 3).Value = Sheets("TABLE1").Cells(ROW2, 1).Value
   
   End If
   
   ROW2 = ROW2 + 1
  Loop
  ROW1 = ROW1 + 1
Loop
   
End Sub

TABLE1

LABEL          ID1    TAG
ABA001_X1      1
ABA001_X2      1 
ABA001_X3      2
ABA001_X4      1
ABA001_X5      1
ABA001_X6      2
ABA002_X1      3
ABA002_X2      4

TABLE2

LABEL          ID1 
ABA001_1        1
ABA001_2        2 
ABA002_1        3
ABA002_2        4

EXPECTED RESULT IN
TABLE1

LABEL          ID1    TAG
ABA001_X1      1       ABA001_1 
ABA001_X2      1       ABA001_1 
ABA001_X3      2       ABA001_2
ABA001_X4      1       ABA001_1 
ABA001_X5      1       ABA001_1 
ABA001_X6      2       ABA001_2
ABA002_X1      3       ABA002_1
ABA002_X2      4       ABA002_1

[Killer42]

I wrote a code as follows to compare 2 tables on diff worksheet.
Each work sheet has about 6000 Rows.
The code works but appears to Work very slow.
Is there a more efficient way to do it.
...

You might be better off using one of Excel's built-in lookup functions to populate the Tag column. For example, I recreated your two tables from the data shown in your post, but in TABLE2 I reversed the order of the two columns. Then I used this formula in cell C2 of TABLE1, I placed this formula =VLOOKUP(B2,TAB LE2!$A$2:$B$5,2 ,FALSE). I copied this cell and pasted it down the rest of the column, and this is the result...

LABEL		ID1	TAG
ABA001_X1 	1	ABA001_1
ABA001_X2 	1	ABA001_1
ABA001_X3 	2	ABA001_2
ABA001_X4 	1	ABA001_1
ABA001_X5 	1	ABA001_1
ABA001_X6 	2	ABA001_2
ABA002_X1 	3	ABA002_1
ABA002_X2 	4	ABA002_2

(edited slightly for formatting here)

[DONE1]

Thank you so much

[Killer42]

Thank you so much

No problem. Let us know whether it works.