How to find duplicate records in sql w3schools

Find duplicate values in SQL efficiently and avoid wasting resources. This article demonstrates how to locate and address duplicate records using SQL's GROUP BY and HAVING clauses.

Database best practices usually dictate having unique constraints (such as the primary key) on a table to prevent the duplication of rows when data is extracted and consolidated.

However, you may find yourself working on a dataset with duplicate rows. This could be because of human error, an application bug, or uncleaned data that’s been extracted and merged from external sources, among other things.

Why fix duplicate values?

Delete duplicate records in sql

They can mess up calculations. They can even cost a company money; for example, an e-commerce business might process duplicated customer orders multiple times, which can have a direct impact on the business’s bottom line.

In this article, we will discuss how you can find those duplicates in SQL by using the and clauses.

Identify Duplicate Values in SQL

First, you will need to define the criteria for detecting duplicate rows.

Is it a combination of two or more columns where

find duplicate records in sql

select duplicate records in sql