Run a query with a LIMIT/OFFSET and also get the total number of rows

📜 The Ultimate Guide to Running a Query with LIMIT/OFFSET and Getting the Total Number of Rows

Are you tired of running separate queries to fetch a limited number of rows and count the total number of rows in your database? 🤔 Don't worry, we've got you covered! In this guide, we'll show you how to run a single optimized query in PostgreSQL that does both tasks efficiently. 👨‍💻

⚡ The Problem

Imagine you're building a web page that displays a list of items fetched from a database table. To implement pagination, you decide to use the LIMIT and OFFSET clauses in your query. However, you also need to show the total number of rows that would be returned by the query without these clauses. How do you achieve this without making multiple database trips? 🤷‍♀️

💡 The Solution

Fortunately, PostgreSQL provides a way to combine the desired functionality in a single query. Here's how you can do it:

SELECT *, COUNT(*) OVER() as total_rows
FROM table
WHERE /* whatever */
ORDER BY col1
LIMIT ? OFFSET ?

Let's break down the query and understand how it solves our problem:

1. SELECT *, COUNT(*) OVER() as total_rows - This selects all columns from the table and calculates the total number of rows using the COUNT(*) OVER() window function. The as total_rows alias assigns a name to the resulting column.

2. FROM table - Replace table with the actual name of your table.

3. WHERE /* whatever */ - Add your desired conditions for filtering the rows.

4. ORDER BY col1 - Specify the column you want to order the results by. Replace col1 with the appropriate column name.

5. LIMIT ? OFFSET ? - Define the number of rows to fetch with LIMIT and the starting point of the fetch with OFFSET. Replace the ? placeholders with the appropriate values in your code.

That's it! 🎉 Running this single query will give you both the limited set of rows for the current page and the total number of rows matching your conditions.

🚀 Optimizing Performance

You might be wondering if running this combined query is as efficient as running the two queries separately. The answer is yes! PostgreSQL is smart enough to optimize this query and avoid extra overhead.

By using the window function COUNT(*) OVER(), the database engine performs the counting operation alongside the regular query execution, resulting in improved performance compared to running the queries individually.

🎯 Call-To-Action

Now that you know how to efficiently fetch a limited set of rows while obtaining the total number of rows, it's time to put it into practice! Update your code to use the combined query and experience the benefits firsthand. Share your success stories or any related questions in the comments below. We'd love to hear from you! 😊📝

📚 Conclusion

Running queries with LIMIT and OFFSET while also retrieving the total number of rows no longer needs to be a challenge. With PostgreSQL's window function COUNT(*) OVER(), you can achieve both tasks efficiently in a single query.

Remember, optimizing your code not only improves performance but also enhances the user experience of your application. So, go ahead and implement this technique in your projects and enjoy the seamless pagination experience!

Happy coding! 💻✨