A Common Table Expression (CTE) is a temporary named result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement. Essentially, it allows you to break down complex queries into smaller, more manageable chunks.

One of the main benefits of using CTEs is that they make your SQL code more readable and easier to maintain. Instead of having a long, convoluted query, you can break it down into smaller, more manageable subqueries that are easier to understand.

Another advantage of using CTEs is that they can improve performance. By using smaller subqueries, you can reduce the amount of data that needs to be processed, which can lead to faster query times.

In order to use a CTE, you first need to define it using the WITH . After that, you can reference it in your query using the name you assigned it.

CTEs are a powerful tool for SQL developers, and they can greatly improve the readability and performance of your code. If you're not already using CTEs in your SQL queries, it's definitely worth taking the time to learn how to use them.