![]() (SELECT store, AVG(amount) AS average_order We can start by calculating the average order amount for each store using a CTE and adding this column to the output of the main query: In our first example, we want to compare the total amount of each order with the average order amount at the corresponding store. This gives us a whole bunch of tools and opportunities. It is possible to have multiple CTEs in one query, reference one CTE within another (i.e., nested CTEs), or even reference a CTE within itself (recursive CTEs). If you are new to CTEs, you may need to check out this article that explains in more detail how CTEs work. After the CTE is defined, we move on to the main query, where we can reference this CTE by its name. Then, we put the AS keyword and include the subquery in parentheses. We start with the WITH keyword followed by the name we assign to the CTE (subquery). CTEs were introduced in SQL to improve the readability and the structure of an SQL statement. Common Table Expressions in SQLĬommon table expressions (CTEs), also called WITH clauses, allow creating named subqueries that are further referenced in the main query. In this article, we will go through several examples to show how SQL CTEs can help you with complex calculations and hierarchical data structures. ![]() Common table expressions (CTEs) were introduced into SQL to improve the readability and the structure of SQL queries, especially those requiring multiple steps to get the necessary output. ![]()
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