Problem: 1789. 员工的直属部门

👨‍🏫 参考题解

Code

select employee_id, department_id
from Employee
where primary_flag = 'Y' # Y 表明是直属部门
or employee_id in (
    select employee_id
    from Employee
    group by employee_id
    having count(employee_id) = 1 # 子查询的结果是 单一部门的员工id集
)