Excel VBA Hidding rows by comparing two Cells - excel

Question

I have a question about how to use a double loop to compare two Cells which are located in different sheets("Sheet1" and "Sheet2").
The condition I want to apply to the Loop is that in case if the two cells are different, the row must be hidden (Applied to the table located in Sheet1). In the contrary case, if the two cells are the same, the row stays as it is by default.
But with the Macro I wrote, it hides all rows that form the Sheet1 table. What could be the reason?
Sub HideRows()
Sheets("Sheet2").Select
Dim NR As Integer
NR = WorksheetFunction.CountA(Range("A1", Range("A1").End(xlDown)))
Sheets("Sheet1").Select
Dim i As Integer, j As Integer
For i = 2 To 10
For j = 1 To NR
If Cells(i, 1) <> Sheets("Sheet2").Cells(j, 1) Then
Rows(i & ":" & i).Select
Selection.EntireRow.Hidden = True
End If
Next j
Next I
End Sub
Sheet1:
Sheet2:
Desired result:

Answer 1

Your task is better described as
Hide all rows on Sheet1 whose column A value does not apear on Sheet2 column A
Using the looping the ranges technique you tried, this could be written as
Sub HideRows()
Dim rng1 As Range, cl1 As Range
Dim rng2 As Range, cl2 As Range
Dim HideRow As Boolean
With ThisWorkbook.Worksheets("Sheet1")
Set rng1 = .Range(.Cells(2, 1), .Cells(.Rows.Count, 1).End(xlUp))
End With
With ThisWorkbook.Worksheets("Sheet2")
Set rng2 = .Range(.Cells(1, 1), .Cells(.Rows.Count, 1).End(xlUp))
End With
rng1.EntireRow.Hidden = False
For Each cl1 In rng1.Cells
HideRow = True
For Each cl2 In rng2.Cells
If cl1.Value2 = cl2.Value2 Then
HideRow = False
Exit For
End If
Next
If HideRow Then
cl1.EntireRow.Hidden = True
End If
Next
End Sub
That said, while this approach is ok for small data sets, it will be slow for larger data sets.
A better approach is to loop Variant Arrays of the data, and build a range reference to allow hiding all required rows in one go
Sub HideRows2()
Dim rng1 As Range, cl1 As Range, dat1 As Variant
Dim rng2 As Range, cl2 As Range, dat2 As Variant
Dim HideRow As Boolean
Dim r1 As Long, r2 As Long
Dim HideRange As Range
With ThisWorkbook.Worksheets("Sheet1")
Set rng1 = .Range(.Cells(1, 1), .Cells(.Rows.Count, 1).End(xlUp))
dat1 = rng1.Value2
End With
With ThisWorkbook.Worksheets("Sheet2")
Set rng2 = .Range(.Cells(1, 1), .Cells(.Rows.Count, 1).End(xlUp))
dat2 = rng2.Value2
End With
rng1.EntireRow.Hidden = False
For r1 = 2 To UBound(dat1, 1)
HideRow = True
For r2 = 1 To UBound(dat2, 1)
If dat1(r1, 1) = dat2(r2, 1) Then
HideRow = False
Exit For
End If
Next
If HideRow Then
If HideRange Is Nothing Then
Set HideRange = rng1.Cells(r1, 1)
Else
Set HideRange = Application.Union(HideRange, rng1.Cells(r1, 1))
End If
End If
Next
If Not HideRange Is Nothing Then
HideRange.EntireRow.Hidden = True
End If
End Sub

Answer 2

#Chjris Neilsen has beaten me to most of what I wanted to mention. Please refer to his comment above. However, there are two things I want to add.
Please don't Select anything. VBA knows where everything is in your workbook. You don't need to touch. Just point.
i and j aren't really meaningful variable identifiers for Rows and Columns. They just make your task that much more difficult - as if you weren't struggling with the matter without the such extra hurdles.
With that out of the way, your code would look as shown below. The only real difference is the Exit For which ends the loop when the decision is made to hide a row. No guarantee that the procedure will now do what you want but the logic is laid are and shouldn't be hard to adjust. I point to .Rows(C).Hidden = True in this regard. C is not a row. It's a column.
Sub HideRows()
' always prefer Long datatype for rows and columns
Dim Rl As Long ' last row: Sheet2
Dim C As Long ' loop counter: columns
Dim R As Long ' loop counter: rows
Rl = WorksheetFunction.CountA(Sheet2.Columns(1))
With Sheet1
For C = 2 To 10
For R = 1 To Rl
' always list the variable item first
If Sheets("Sheet2").Cells(R, 1).Value <> .Cells(C, 1).Value Then
.Rows(C).Hidden = True
Exit For
End If
Next R
Next C
End With
End Sub