列出员工人数最少的部门名称

Question

有两个表，employee和dept：

如何加入这两个表并选择员工人数最少的部门？

Answer 1

如果您提供了表格结构，那么最好回答。

但试一试：

SELECT deptname 
FROM dept 
WHERE deptid = (SELECT distinct deptid 
                FROM employee
                ORDER BY COUNT(dept) limit 1);

Answer 2

我只是回答，因为MIN不需要而且LIMIT不是Oracle：

select d.*
from (select deptid, count(*) as cnt
      from employees e
      group by deptid
      order by count(*) asc
     ) d
where rownum = 1;

在Oracle 12C +中，您不需要子查询：

      select deptid, count(*) as cnt
      from employees e
      group by deptid
      order by count(*) asc
      fetch first 1 row only;

Answer 3

请尝试以下方法......

SELECT deptid,
       deptname,
       employeeCount
FROM
(
    SELECT dept.deptid AS deptid,
           dept.deptname,
           COUNT( dept.deptid ) AS employeeCount
    FROM dept
    JOIN employee ON dept.deptid = employee.deptid
    GROUP BY dept.deptid,
             dept.deptname
)
GROUP BY deptid
HAVING employeeCount = MIN( employeeCount );

此语句以在共享字段dept上将employee加入deptid的内部查询开始。然后，它按部门对结果行进行分组，并返回部门的id和name的外部查询以及该部门的员工数。

外部查询再次按部门对数据进行分组，然后选择员工人数等于最低雇员人数的部门的详细信息。

如果您有任何问题或意见，请随时发表评论。

Answer 4

嗨:)所以我的答案有点难看，并且充满了嵌套查询。但我测试了它，它对我有用......

-- First I created a couple of test tables and added a few records 
drop table dept;
drop table employee;
create table dept (deptid number primary key, deptname varchar(20));
create table employee(employee_id number primary key, names varchar(20),
deptid number,foreign key (deptid) references dept(deptid));
insert into dept values(1,'HR');
insert into dept values(2,'Finance');
insert into dept values(3,'IT');
insert into employee values(1,'Tina',1);
insert into employee values(2,'Rob',1);
insert into employee values(3,'Lisa',1);
insert into employee values(4,'Will',2);
insert into employee values(5,'Lina',2);
insert into employee values(6,'Ethel',2);
insert into employee values(7,'Trevor',1);
insert into employee values(8,'Alanea',1);
insert into employee values(9,'Matthew',1);
insert into employee values(10,'Maddie',3);
insert into employee values(11,'Anna',1);
-- According to the added records, the answer we are looking for should be
the department name IT

-- select the department name from department table
select d.deptname from dept d, 
/* This is where it gets ugly - basically, it counts the number of
employees in each department, then finds the id of the department that had
the smallest count */
(select deptid from 
(select count(deptid) as counter, deptid from employee group by deptid) 
where counter =( select min(counter)from 
(select count(deptid) as counter, deptid from employee group by deptid))) minid
-- join the tables using deptid
where d.deptid = minid.deptid;

即使我更改记录以使财务成为正确答案，此查询也为我提供了正确的答案。 如果您有任何问题，请通过评论大喊大叫：）

Answer 5

select department_name, count(employee_id)
from department d
inner join employee e
on d.employee_id = e.employee_id
having count(employee_id) = 
(
select min(count(employee_id)) /*This query returns minimum count*/
from department d
inner join employee e
on d.employee_id = e.employee_id
group by department_name
)
group by department_name;

Answer 6

WITH temp AS (SELECT e1.department_id, count(e1.employee_id) emp_count FROM hr.employees e1 GROUP BY e1.department_id) SELECT d1.department_name, t1.emp_count employee_count FROM temp t1 ,hr.departments d1 WHERE t1.department_id = d1.department_id(+) AND NOT EXISTS (SELECT 1 FROM temp t2 WHERE t2.emp_count < t1.emp_count) ORDER BY 2,1 ;