Finding and Removing Duplicates

When working with datasets, one of the most common structural problems is duplicate rows. These are records that appear more than once and usually represent the same data.

Duplicates often occur when data is merged from multiple sources, imported several times, or entered manually. At first glance, everything may look fine, but duplicates can seriously distort your analysis. For example, totals may become inflated, and reports may show incorrect results.

Finding Duplicates

Before deleting anything, it's important to first identify duplicates.

One way to do this is using the COUNTIF function:

=COUNTIF(A:A, A2)

This formula counts how many times a value appears in a column. If the result is greater than 1, it means the value is duplicated.

Removing Duplicates

Once duplicates are identified, Excel provides a built-in tool to remove them.

You can select the table, go to the Data tab, and use Remove Duplicates. Excel will scan the selected columns and remove repeated rows automatically.

Excel compares selected columns row by row. If it finds identical values, it keeps one instance and removes the rest. This helps ensure that each record appears only once.

Task

Find duplicate records in the dataset.

You may notice that the Order ID column contains duplicates. Identify these duplicate records first, then completely remove the duplicated rows using the Remove Duplicates tool.