In MySQL, the WITH clause creates a temporary named result set known as a Common Table Expression (CTE). It allows you to define and reference a subquery in the main query.

The syntax for using the WITH clause in MySQL is as follows:

WITH cte_name AS (
SELECT column1, column2, …
FROM table_name
WHERE conditions
)
SELECT column1, column2, …
FROM cte_name
WHERE conditions

In the above syntax, the subquery inside the WITH clause is defined and given a name (cte_name). The main query then uses this CTE to retrieve data.

Using the WITH clause has several benefits, including:

• It simplifies complex queries by allowing you to define subqueries that can be reused multiple times in the main query.
• It improves query performance by reducing the need for nested subqueries.
• It makes queries easier to read and maintain.

Note that not all versions of MySQL support the WITH clause. As of MySQL 8.0, the WITH clause is supported.