What is the purpose of the LIMIT clause?

The LIMIT clause in SQL is used to restrict the number of rows returned by a query. It allows developers to specify a maximum number of results to retrieve, which is particularly useful when working with large datasets or optimizing performance. For example, SELECT * FROM orders LIMIT 10; would return only the first 10 rows from the orders table. This is often applied in scenarios like pagination, sampling data for testing, or reducing query execution time by avoiding unnecessary data retrieval.

A key use case for LIMIT is implementing pagination in applications. When displaying data across multiple pages, combining LIMIT with OFFSET allows fetching specific subsets of results. For instance, SELECT * FROM products LIMIT 20 OFFSET 40; would skip the first 40 rows and return rows 41–60, effectively showing the third page of results if each page displays 20 items. Additionally, LIMIT improves performance during development and testing. Running SELECT * FROM large_table LIMIT 1; quickly verifies a query’s syntax or logic without waiting for a full dataset to load, which is especially valuable when debugging.

However, using LIMIT effectively requires attention to ordering and database compatibility. Without an ORDER BY clause, the rows returned by LIMIT may be unpredictable because databases don’t guarantee a default sort order. For example, SELECT * FROM employees ORDER BY hire_date DESC LIMIT 5; ensures you get the five most recently hired employees. It’s also important to note that syntax varies across database systems: MySQL and PostgreSQL use LIMIT, while SQL Server uses TOP or OFFSET FETCH. Developers should adapt their queries to the target database to avoid errors.