题解 | 汇总各个部门当前员工的title类型的分配数目

SELECT t1.dept_no, dept_name, title, COUNT(title) AS count
FROM departments t1
LEFT JOIN dept_emp t2
USING (dept_no)
LEFT JOIN titles t3
USING (emp_no)
GROUP BY t1.dept_no, t3.title
ORDER BY t1.dept_no ASC, t3.title ASC;