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';