Excel Compare Columns: Identifying Duplicates

How To Compare Columns To Find Duplicates

You have 3 columns with data and you want to highlight duplicates.

First select whole table.

Go to the Ribbon. Home tab > Styles section. Click Conditional Formatting > Highlight Cell Rules > Duplicate Values

Dialog box appears. Choose how Excel will highlight duplicates.

Excel highlights duplicates from your table.

Template

Further reading: 
Basic concepts 
Getting started with Excel
Cell References