select 
  dept,
  userid,
  sal,
  percent_rank() over (order by sal) as rn1, --分组内
  rank() over (order by sal) as rn11, --分组内的rank值
  sum(1) over (partition by null) as rn12, --分组内总行数
  percent_rank() over (partition by dept order by sal) as rn2,
  rank() over (partition by dept order by sal) as rn21,
  sum(1) over (partition by dept) as rn22 
from cookie.cookie3;

rn1: rn1 = (rn11-1) / (rn12-1) 
       第一行,(1-1)/(5-1)=0/4=0
       第二行,(2-1)/(5-1)=1/4=0.25
       第四行,(4-1)/(5-1)=3/4=0.75
rn2: 按照dept分组，
     dept=d1的总行数为3
     第一行，(1-1)/(3-1)=0
     第三行，(3-1)/(3-1)=1