嘿，我正在尝试使用 rank() 但我运气不好，

select t.orig, t.id, count(*) as num_actions, 
rank() over (partition by t.orig order by count(*) desc) as rank
from sample_table t
where rank < 21 
and t.month in (201607,20608,201609,201610,201611,201612) 
and t.orig in (select tw.pageid from tw_sample as tw limit 50) 
group by t.orig, t.id

我一直在想，
失败：semanticexception[错误10004]：行4:6无效的表别名或列引用“rank”
我的目标是为每一位选手争取前20排 t.orig 基于 count(*) 参数。
如果你也能解释一下我哪里出错了，这样我就可以从中吸取教训，那将不胜感激。