Question

编写一个查询以显示部门名称和每个部门中的人员计数，如果人员不存在，则将计数显示为0。为人员计数命名为staff_count。根据部门名称对结果进行排序。

这就是我尝试过的。

select department_name,count(*) as staff_count
from left join staff on department.department_id=staff.staff_id
group by department_name order by department_name;

我认为我的代码中缺少一些内容。

Answer 1

我将您的查询写为：

SELECT
    d.department_name,
    d.department_id,
    COUNT(s.staff_id) AS cnt
FROM department d
LEFT JOIN staff s
    ON d.department_id = s.department_id
GROUP BY
    d.department_name,
    d.department_id
ORDER BY
    d.department_name;

您想从department到staff表中进行合并，以将每个部门记录乘以其包含的员工人数。我们计算员工价值，这可以处理给定部门没有员工的情况。

请注意，我假设department_id是两个表中联接列的名称。如果不是，则相应地修改上面的查询。

Answer 2

SELECT
    d.department_name,
    COUNT(s.staff_id) AS staff_count
FROM department d
LEFT JOIN staff s
    ON d.department_id = s.department_id
GROUP BY
    d.department_name,
    d.department_id
ORDER BY
    d.department_name;

Answer 3

如果您想以其他方式执行此操作。然后，您可以尝试以下代码。

1 select d.department_name,count(s.staff_id) as staff_count
2 from department d,staff s
3 where d.department_id=s.department_id(+)
4 group by department_name
5 order by department_name;

Answer 4

从部门中选择部门名称，人数（学生姓名）作为学生人数自然加入学生按部门名称分组按部门名称排序；

Answer 5

select 
    department_name,
    nvl(count(staff_id,0)as staff_count 
from department
inner join staff 
    on department.department_id=staff.department_id
group by department_name
order by department_name

编写查询以显示部门名称和每个部门的员工人数，如果不存在员工，则将其显示为0

5 个答案: