题解 | #获取所有非manager的员工emp_no#

解1：not exists + 子查询

select
    emp_no
from employees e

where not exists (
    select
        1
    from dept_manager

    where emp_no = e.emp_no
)

解2：not in + 子查询

select
    emp_no
from employees e

where emp_no not in (
    select
       emp_no
    from dept_manager
)

解3：left join

select
    e.emp_no
from employees e
left join dept_manager dm on dm.emp_no = e.emp_no
where dm.emp_no is null