postgresql data sorting

to sort

-- 排序的时候null是最大的值(看一下)
select
employee_id,manager_id
from employees
 order by manager_id desc;

-- nulls first使null值排在第一位
select
employee_id,manager_id
from employees
 order by manager_id nulls first;

-- nulls first使null值排在最后一位
select
employee_id,manager_id
from employees
 order by manager_id nulls last;

Summarize