题解 | #汇总各个部门当前员工的title类型的分配数目#

答案不知道为什么与正确答案不一样，无奈之下，只能在ORDER BY e.dept_no的基础之上在加入t.title。

SELECT e.dept_no, d.dept_name, t.title, COUNT(t.title) as count
FROM
    titles as t,
    dept_emp as e,
    departments as d
WHERE
    t.emp_no = e.emp_no and
    e.dept_no = d.dept_no and
    e.to_date = '9999-01-01' and
    t.to_date = '9999-01-01'
GROUP BY d.dept_no, t.title
ORDER BY e.dept_no, t.title ASC