2025.01.03 쿼리문

문제) d001부서의 staff의 평균 나이는? 

SELECT 
    AVG(YEAR(CURDATE()) - YEAR(e.birth_date)) AS average_age
FROM 
    dept_emp de
JOIN 
    employees e ON de.emp_no = e.emp_no           
JOIN 
    titles t ON e.emp_no = t.emp_no                
WHERE 
    de.dept_no = 'd001'                           
    AND t.title = 'Staff'                       
    AND t.to_date = '9999-01-01';