What is a CTE?

A Common Table Expression (CTE) is a temporary result set in SQL that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement. It is defined using the WITH clause and can simplify complex queries by breaking them into more manageable parts. CTEs can also be recursive, allowing for operations on hierarchical data.

Here’s a basic structure of a CTE:

WITH CTE_Name AS (
    SELECT column1, column2
    FROM table_name
    WHERE condition
)
SELECT *
FROM CTE_Name;

In this example, CTE_Name is defined to hold the result of the query, which can then be used in subsequent SQL statements.