题解 | 汇总各个部门当前员工的title类型的分配数目

-- 一表多用
# select d.dept_no, d.dept_name, t.title, count(t.title)
# from departments as d, titles as t, dept_emp as de

# where t.emp_no = de.emp_no -- 职位与员工关系匹配
# and de.dept_no = d.dept_no -- 员工与部门关系匹配
# and t.to_date = '9999-01-01'

# group by d.dept_no, d.dept_name, t.title

# order by dept_no, dept_no;

select d.dept_no, d.dept_name, t.title, count(t.title)
from dept_emp as de
inner join titles as t on de.emp_no = t.emp_no
inner join departments as d on de.dept_no = d.dept_no
group by d.dept_no, d.dept_name, t.title
order by dept_no, dept_no;