Have you used the EXISTS operator in SQL queries?

The EXISTS operator in SQL is used to check for the existence of rows that satisfy a subquery. It returns TRUE if the subquery returns at least one row, and FALSE if it does not.

Example usage:

SELECT * FROM employees e
WHERE EXISTS (
    SELECT 1 FROM departments d
    WHERE d.id = e.department_id AND d.name = 'Sales'
);

This example selects all employees who work in the "Sales" department. EXISTS is efficient for checking the presence of related data without needing to return the data itself.