Excel - check duplicates in two columns

How can I check for duplicates across two or more columns - please see the following column examples:

First Name                 Last Name                 Date of Birth

Thank you
exp vgAsked:
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Thibault St john Cholmondeley-ffeatherstonehaugh the 2ndCommented:
I usually create a formula in a further column.  For example, if your columns are a, b and c them in d1 I add (sulynrltax will be close but may need adjusting, I'm on my phone).
= if (or ((a2=a1), (b2=b21, (c2=c1)),"","duplicate")

 copy this all the way down the d column.
you will need to sort a, then b then c into an order to check all columns.

or to check an exact duplicate across all columns change the or to and.
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Thibault St john Cholmondeley-ffeatherstonehaugh the 2ndCommented:
sorry my phone has its own ideas about Autocorrupting.
the odd word is supposed to be Syntax
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Thibault St john Cholmondeley-ffeatherstonehaugh the 2ndCommented:
and of course b21 should read b2
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Thibault St john Cholmondeley-ffeatherstonehaugh the 2ndCommented:
nope, b1. I hope you can follow that. any questions please ask.

the result will be a clear column d if there are no dups and the word duplicate if there are any.
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Rodney EndrigaData AnalystCommented:
You can use a formula like this one to count the # of duplicates among multiple columns (insert at Cell D2):
=SUMPRODUCT(($A:$A=A2)*($B:$B=B2)*($C:$C=C2))

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This assumes your lookup data is in Columns A, B, C, respectively. You will have to adjust the row ranges according to your data.
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