Question

我有

employees table(id,f_name,l_name,salary,dept_id,manager_id)

departments table(id,dept_name,manager_id)

我想展示dept_name，其manager_id，经理的l_name以及在单个表格中在各自经理下工作的员工数量。

Answer 1

试试这个：

SELECT dept.dept_name, dept.manager_id, emp.l_name, emp_count.empcount 
FROM departments AS dept 
INNER JOIN (SELECT COUNT(*) AS empcount, manager_id FROM employees GROUP BY manager_id) AS emp_count ON dept.manager_id = emp_count.manager_id
INNER JOIN employees AS emp ON dept.manager_id = emp.id

或者这个：

SELECT dept.dept_name, dept.manager_id, emp.l_name, emp_count.empcount 
FROM departments AS dept 
INNER JOIN (SELECT COUNT(*) AS empcount, dept_id FROM employees GROUP BY manager_id) AS emp_count ON dept.dept_id = emp_count.dept_id
INNER JOIN employees AS emp ON dept.manager_id = emp.id

第一个是引用manager_id，第二个是引用dept_id。从两者中可以得到相同的结果。我通过为员工数量创建子查询并将其链接到部门来实现这一目标。

这里是SQL Server 2008 Fiddle。

Answer 2

您可以使用简单查询执行此操作，但是，您应该删除employees表中的manager_id，并使用员工记录ID作为标识符。

Select dept.dept_name, dept.manager_id, (select e.l_name from employees as e where e.id = dept.manager_id), count(select em.id from employees as em where dept.id = em.dept_id) FROM departments as dept

但这应该有效，您没有提供您正在使用的特定数据库。如果您更新了问题或告诉了什么数据库，我可以编辑该数据库，如果它不起作用。

Answer 3

检查

    select d.deptname, d.managerid, e.fname, (select COUNT(*) 
                                            from employees 
                                            where managerid = d.managerid and 
                                            managerid <> id and
                                            depid = d.id
                                            group by managerid) NoofEmps
from departments d join employees e on d.managerid = e.id

字段名称可能与您提到的不完全相同。

Answer 4

您可以通过此correlated subquery来获取计数。休息你可以选择使用join。这可能会对你有所帮助

 SELECT  D.dept_name,
            D.manager_id,
            E.l_name,
            (SELECT COUNT(*) 
                     FROM employees 
                     WHERE manager_id=D.manager_id) AS numberOfEmployees
 FROM   departments D INNER JOIN employees E ON D.manager_id=E.id

Answer 5

这是您可以考虑的另一种解决方案

SELECT D.dept_name as [Department Name],
E.manager_id as [Manager ID],
E.l_name as [Last Name],
(SELECT COUNT(*) FROM employees EM WHERE EM.manager_id = E.id) as [Employee Count]
FROM departments D
INNER JOIN employees E on D.manager_id = E.manager_id

如何为员工和部门表编写SQL查询

5 个答案: