-- rank()排名是不連續(xù)的，出現(xiàn)同名的排序序號(hào)會(huì)相同(比較常規(guī)的排序)，且序號(hào)會(huì)斷開(kāi)

select 
employee_id
,last_name
,department_id
,salary
,rank() over(partition by department_id order by salary desc) 
from employees

-- row_number()排名是連續(xù)的,出現(xiàn)同名的序號(hào)仍然會(huì)連續(xù)(用來(lái)記錄次數(shù)比較實(shí)用)，且不會(huì)跳躍

select 
employee_id
,last_name
,department_id
,salary
,row_number() over(partition by department_id order by salary desc) 
from employees

-- dense_rank()排名是連續(xù)的，出現(xiàn)同名的序號(hào)會(huì)相同，且不會(huì)跳躍（用的比較少的，單純需要排名且存在并列也不跳躍）

select 
employee_id 
,last_name 
,department_id 
,salary 
,dense_rank() over(partition by department_id order by salary desc) 
from employees 

-- ntile()根據(jù)排序指定數(shù)量進(jìn)行分區(qū)編號(hào)（分區(qū)編號(hào)排序）

select 
employee_id 
,last_name 
,department_id 
,salary 
,ntile(3) over(partition by department_id order by salary desc) 
from employees