Question

我的hive表（tab1）结构：

people_id,time_spent,group_type
1,234,a
2,540,b
1,332,a
2,112,b

以下是我正在尝试执行的查询但收到错误（“UDAF'还不支持的地方'sum'”）：

select people_id, sum(case when group_type='a' then time_spent else 0 end) as a_time, sum(pow(a_time,2)) as s_sq_a_time,sum(case when group_type='b' then time_spent else 0 end) as b_time, sum(pow(b_time,2)) as s_sq_b_time from tab1 group by people_id;

是否可以从Hive中的相同select语句引用聚合列？我也在下面提到链接，但它没有工作： http://grokbase.com/t/hive/user/095tpdkrgz/built-in-aggregate-function-standard-deviation#

Answer 1

为表名设置别名，并在访问列时使用表别名。

E.g。

select startstation, count(tripid) as a
from 201508_trip_data as t
group by t.startstation

注意't'是表的别名，我使用t.startstation访问

Answer 2

您必须使用派生表来引用a_time和b_time

select a_time, b_time,
pow(a_time,2) as s_sq_a_time,
pow(b_time,2) as s_sq_b_time
from (
    select people_id,
    sum(case when group_type='a' then time_spent else 0 end) as a_time,
    sum(case when group_type='b' then time_spent else 0 end) as b_time 
    from tab1 group by people_id
) t1

Hive Query中使用聚合列

2 个答案: