Question

我有2个表，一个表存储人员的详细信息（列为staff_id，staff_name，department_id），另一个表存储部门的详细信息（列为department_id，department_name，department_block_num）。

我需要编写一个查询来显示部门名称和每个部门的人员计数，如果不存在人员显示计数为0。

这是代码

Select department_name, 
        case department.department_id 
             when department.department_id=staff.department_id then count(staff_name)  
        else 0 end staff_count 
From department, staff 
Group by department_name 
order by department_name;

Answer 1

您正在寻找LEFT JOIN和汇总查询：

select d.department_id, d.department_name, 
       count(s.department_id) as staff_count 
from department d left join
     staff s
     on d.department_id = s.department_id
group by d.department_id, d.department_name

在Oracle上运行代码时遇到缺少关键字错误

1 个答案: