![]() ![]() In the examples below, we will be exploring both these scenarios using a simple customer order database. ![]() Is it a combination of two or more columns where you want to detect duplicate values, or are you simply searching for duplicates within a single column? In this article, we will discuss how you can find those duplicates in SQL by using the GROUP BY and HAVING clauses.įirst, you will need to define the criteria for detecting duplicate rows. 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. Why fix duplicate values? They can mess up calculations. 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. ![]() However, you may find yourself working on a dataset with duplicate rows. It contains over 80 hands-on exercises to let you practice different SQL constructions, from simple single-table queries, through aggregation, grouping, and joining data from multiple tables, to complex topics such as subqueries.ĭatabase 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. The best way to practice GROUP BY and HAVING clauses is 's interactive SQL Practice Set course. Learn how to find and fix duplicate values using SQL’s GROUP BY and HAVING clauses. Duplicate records waste time, space, and money. ![]()
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