Excel - finding duplicate values over multiple columns - excel

Question

I have a data set containing phone numbers three different users. Each one is its own column in Excel. Eg Alice called the numbers in A:A, Bob called the numbers in B:B and Carol called the numbers in C:C (each column is a different length).
I am trying to determine which phone numbers all 3 have called. I have used unique to filter out duplicates from each list and I know how to find duplicate values over two columns using conditional formatting. But how do I find values that ONLY appear in all three columns?
Clarification:
A mockup of the data is as follows (I can't give out the real data):
| 1 | 5656 | 6464 | | | |-----|------|------|---|---| | 2 | 1 | 456 | | | | 456 | 2 | 2 | | | | 345 | 800 | 1 | | |
I want excel to look through the three columns and find any values which are common to all 3 columns and highlight them.

Answer 1

Let's assume the input data is in the range of A2:C7, you can try the following formula in E2:
=LET(rng, A2:C7, ux, UNIQUE(TOCOL(rng,1)),DROP(REDUCE("", ux, LAMBDA(ac, x,
LET(cmp, N(rng=x), ones, SEQUENCE(,ROWS(cmp),1,0), IF(SUM(MMULT(ones, cmp))=3,
VSTACK(ac,x), ac)))),1))
A simplified approach can be achieved using COUNTIFS:
=LET(rng, A2:C7, ux, UNIQUE(TOCOL(rng,1)), FILTER(ux, COUNTIFS(rng,ux)=3))
Here is a sample input data and the corresponding output. Highlighted the numbers the formula should return (see conditional formatting formula below):
The previous solutions assumes there are no repeated numbers per column in the input range (rng). Under this assumption you can define a Conditional formatting as follow:
=SUM(N(A2=$A$2:$C$7))=3
If the number can be repeated within a given column, then the first formula can be adjusted as follow:
=LET(rng, A2:C7, ux, UNIQUE(TOCOL(rng,1)),DROP(REDUCE("", ux, LAMBDA(ac,x,
LET(cmp, N(rng=x), ones, SEQUENCE(,ROWS(cmp),1,0),
IF(SUM(N(MMULT(ones, cmp) >= 1))=3, VSTACK(ac,x), ac)))),1))
Both solutions should work regardless of the number of rows of the input columns. The second input argument of TOCOL(1) ensures empty cells are not taken into account.

Answer 2

You will need to change the ranges, I used just 3 rows to test it.
Sub FindCommonNumbers()
Dim dict As Object
Dim rngAlice As Range, rngBob As Range, rngCarol As Range
Dim cell As Range
Dim phone As Variant
' Create a new dictionary object
Set dict = CreateObject("Scripting.Dictionary")
' Set the range for each user's phone numbers
Set rngAlice = Range("A1:A3")
Set rngBob = Range("B1:B3")
Set rngCarol = Range("C1:C3")
' Add the phone numbers from the first column to the dictionary
For Each cell In rngAlice
dict(cell.Value) = 1
Next cell
' Check the phone numbers in the second column against the dictionary
For Each cell In rngBob
If dict.exists(cell.Value) Then
dict(cell.Value) = dict(cell.Value) + 1
End If
Next cell
' Check the phone numbers in the third column against the dictionary
For Each cell In rngCarol
If dict.exists(cell.Value) Then
dict(cell.Value) = dict(cell.Value) + 1
End If
Next cell
' Print the phone numbers that appear in all three columns
For Each phone In dict.Keys()
If dict(phone) = 3 Then
Debug.Print phone
End If
Next phone
End Sub