Common Table Expressions (CTEs) in SQL

 Common Table Expressions (CTEs) in SQL

CTEs are temporary result sets that are defined within an SQL statement. CTEs can be used to simplify complex queries and improve performance. Here's an example:

vbnet

WITH sales_employees AS (

    SELECT name, age

    FROM employees

    WHERE department = 'Sales'

)

SELECT name, age

FROM sales_employees

WHERE age > 30;

In this example, we're defining a CTE called "sales_employees" that selects the name and age of all employees who work in the Sales department. We can then use this CTE in the main query to filter out employees under the age of 30.