题解 | #统计各个部门的工资记录数#
统计各个部门的工资记录数
http://www.nowcoder.com/practice/6a62b6c0a7324350a6d9959fa7c21db3
select d.dept_no, d.dept_name,
sum(if(s.salary is not null,1,0)) as sum
from departments as d
inner join dept_emp as de
on d.dept_no = de.dept_no
inner join salaries as s
on de.emp_no = s.emp_no
group by d.dept_no
order by d.dept_no
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