If you’re working with large datasets in PostgreSQL, you might find yourself needing to limit the number of rows returned in a query. Whether you’re trying to reduce the amount of data you have to work with or simply trying to speed up your queries, limiting the number of rows returned is a useful tool to have in your PostgreSQL toolbox.
👋 Check out our easy to use desktop GUI for PostgreSQL
Beekeeper Studio is a truly cross-platform PostgreSQL GUI with a clean, uncluttered interface. Write SQL, edit data, alter tables, and more!
Available for MacOS, Linux, and Windows.
In this post, we’ll cover the basics of limiting the number of rows returned in PostgreSQL, including a few different ways to do it and some code examples to help you get started.
The LIMIT Clause
The simplest and most straightforward way to limit the number of rows returned in PostgreSQL is to use the
LIMIT clause. The
LIMIT clause allows you to specify the maximum number of rows that you want returned from your query.
Here’s an example of how to use the
SELECT * FROM customers LIMIT 10;
This query will return the first 10 rows from the
customers table. Note that the order in which the rows are returned depends on the order specified in the
ORDER BY clause (if one is present). If no
ORDER BY clause is present, the order of the rows is undefined.
Using LIMIT With OFFSET
In addition to the
LIMIT clause, you can also use the
OFFSET clause to skip a specified number of rows before starting to return results. For example:
SELECT * FROM customers LIMIT 10 OFFSET 20;
This query will return the next 10 rows after skipping the first 20 rows in the
Pagination With LIMIT and OFFSET
By combining the
OFFSET clauses, you can implement paging and navigate through your data in a more efficient way. For example:
SELECT * FROM customers LIMIT 10 OFFSET (10 * (current_page - 1));
This query will return 10 rows for each page, with the
current_page variable determining which page to return. You can change the value of
current_page to navigate through different pages of data.
Limiting Rows Based on a Condition
In some cases, you might want to limit the number of rows returned based on a condition. For example, you might want to return the top 10 customers with the highest sales. To do this, you can use a subquery:
SELECT * FROM ( SELECT *, ROW_NUMBER() OVER (ORDER BY sales DESC) AS row_num FROM customers ) subquery WHERE row_num <= 10;
This query uses the
ROW_NUMBER() function to assign a unique number to each row in the result set, based on the
sales column. The outer query then filters the rows to only include those with a
row_num of 10 or less.
Limiting the number of rows returned in PostgreSQL is a useful technique for managing large datasets. Whether you’re trying to reduce the amount of data you have to work with, speed up your queries, or implement paging, the
OFFSET clauses provide a simple and flexible way to achieve your goals. And by combining them with other techniques such as subqueries, you can implement even more complex and sophisticated solutions.
More Postgresql Articles
- PostgreSQL CREATE TABLE Walkthrough With Examples
- PostgreSQL How To Use Schemas
- PostgreSQL CONSTRAINT Walkthrough
- Running Postgres in Docker for Local Development
- 7 Must-Have Tools For Developers That Use PostgreSQL
- PostgreSQL - Change The Type Of A Column, A Walkthrough With Examples
- Postgres Client For Ubuntu