例如，如下所示（表的两次扫描：一次在子查询中查找max date，另一次在主查询中）：

select * 
  from mytable
where as_of_date in (select max(as_of_date) from mytable where as_of_date between first_day(add_months(current_date, -1)) and  last_day(add_months(current_date, -1))

或者像这样（单扫描+分析函数）

select col1 ... colN
from
(
     select t.*, rank() over (partition by month (t.as_of_date) order by t.as_of_date desc) rnk
      from mytable t 
     where --If you have partition on date, this WHERE may improve performance 
          t.as_of_date between first_day(add_months(current_date, -1)) and  last_day(add_months(current_date, -1))
)s 
where rnk=1