您可以聚合以获得预期答案：

select cust_id,
   case
     when max(logindate) > current_date - 7  -- active last week
       then 'Returning WAU' 
     when max(logindate) > current_date - 30 -- not active last week, but active within last 30 days
       then 'WAU'
     else 'Reactivated WAU'                  –- not seen in 30+ days
   end
from tab
group by 1

关于滞后问题，在您重写之前，已在16.10中引入：

lag(logindate, 1)
over (partition by cust_id
      order by col asc) as lag_ind

max(logindate)
over (partition by cust_id
      order by col asc
      rows between 1 preceding and 1 preceding) as lag_ind

提示：不要在olap函数中使用order by 1，这里是文本值1，而不是第一列。