sql - 如何显示部门详细信息以及每个部门的员工人数？

Question

从员工部门架构如何获取每个部门的详细信息（部门 ID、部门名称）以及每个部门的员工人数。

Answer 1

尝试这个

select dept.deptId,
   deptName,
   count(emp.empid) as numb_of_emps
   from department dept inner join employee emp
   on dept.deptid = emp.deptid
   group by dept.deptid

Answer 2

你可以把它当作 - （正如 Russell Dias 所建议的那样）

select d.deptId,
       deptName,
       count(e.empid) "number of employees"
from department d, employee e
where d.deptid = e.deptid
group by d.deptid,d.deptname

Answer 3

select d.deptno,dname,count(e.empno) "No of Emp"
from dept d, emp e 
where d.deptno = e.deptno
group by d.deptno,d.dname

Answer 4

如果您不需要实际的部门详细信息，而只需要部门名称，则可以进一步简化，如下所示：

SELECT department_name, COUNT(*) AS "Number of employees" 
FROM employees group by department;

Answer 5

SELECT department_name,COUNT(*) FROM employees a,departments b
where a.department_id=b.department_id
group by department_name;

Answer 6

您可以使用内部联接：

Select  e.EmployeeName,
        d.DepartmentName,
        count(d.DepId)As Total_no_of_Employees
From Department d
Inner join Employee e 
    On d.DepId = e.EmpID
Groub By DepartmentName, Total_no_of_Employees

Answer 7

select d.deptno, d.dname, count(e.empno) "Number of employees"
from dept d, emp e
where d.deptno = e.deptno
group by d.deptno,d.dname;