Use of NTILE in sql server

create table #temp1

(

userid int

)

insert into #temp1

select 12

union all select 13

union all select 13

union all select 14

union all select 14

union all select 15

union all select 19

select * from #temp1

select userid,ntile(3) over(order by userid) as final

from #temp1

--It randomly divides