Question

我正在尝试解决一个简单的问题，但我正在抓住细节。

我有2张桌子，一张有员工，另一张有部门。我的问题：我正在尝试检查哪个部门拥有最多员工，并仅输出该特定部门。

到目前为止，我有：

select count(*) Number_of_employees
      from department d, employee e
      where d.department_id = e.department_id
      group by department_name

输出：

NUMBER_OF_EMPLOYEES    
---------------------- 
2                      
4                      
3                      
3                      
3

我的目标是只输出员工最多的部门，即4名员工的部门。

我尝试使用MAX和JOIN，但我对加入并不是很好，所以任何建议都将不胜感激。

Answer 1

@Zsolt Botykai

我认为这是正确的，除了需要DESC的顺序，我认为你不能在查询中引用number_of_employees。（无论如何你不能在oracle中）。

  select department_name 
  from
     (select department_name
            ,number_of_employees
      from  
        ( select department_name, count(*) Number_of_employees
          from department d, employee e
          where d.department_id = e.department_id
          group by department_name) 
      order by Number_of_employees DESC) 
  where rownum = 1

Answer 2

你可以这样做以避免rownum：

select 
      max(d.department_name) keep (dense_rank first order by count(1) desc) as department_name
      , count(1) as number_of_employees
    from employee e
    inner join department d on (e.department_id = d.department_id)
    group by d.department_name
    ;

Answer 3

 select department_name from 
        ( select department_name, count(*) Number_of_employees
            from department d, employee e
           where d.department_id = e.department_id
           group by department_name
           order by 2 desc ) 
  where rownum = 1

应该这样做。

HTH

选择最大值

3 个答案: