select d.deptno, d.dname, t.人数
from dept d, (
  select count(*) 人数, deptno
  from emp
  where deptno in (
    select deptno
    from emp
    where ename = 'KING'
  )
  group by deptno
) t
where d.deptno = t.deptno;

select d.dname, d.deptno, t2.*
from dept d,(
  select t.人数, t.deptno
  from (
    select count(*) 人数,deptno
    from emp
    group by deptno
  ) t
  where t.deptno in (
    select deptno
    from emp
    where ename = 'KING'
  )
) t2
where d.deptno = t2.deptno;

select e.deptno 部门号, d.dname 部门名称, (
  select count(*)
  from (
    select deptno
    from emp
    where deptno in (
      select deptno
      from emp
      where ename = 'KING'
    )
  )
) 人数
from emp e, dept d
where e.deptno = d.deptno and e.ename = 'KING';