Bigquery：运行 多次查询基于不同的 date_trunc 并合并结果，而不是多个 UNION ALL

Question

我希望从核心 table 中提取和合并类似的聚合，但在时间段截断方面有所不同。例如，我通常会这样做：

with base as (
  select 
    event_datetime
    , event_location
    , event_uuid
  from events_table
)

select
  date_trunc(event_datetime, day) as day
  , "day" as period_type
  , event_location
  , count(distinct event_uuid) as number_events
from base
group by day, event_location

union all

select
  date_trunc(event_datetime, week) as week
  , "week" as period_type
  , event_location
  , count(distinct event_uuid) as number_events
from base
group by week, event_location

union all

select
  date_trunc(event_datetime, week) as month
  , "month" as period_type
  , event_location
  , count(distinct event_uuid) as number_events
from base
group by month, event_location

有谁知道是否有办法避免必须维护三个单独的子查询，并让一个子查询根据不同的 date_trunc 重新运行并合并结果（产生与代码相同的输出以上）？我知道我以前的公司有人做到了这一点，但我不知道是怎么做到的。

谢谢！

Answer 1

考虑以下方法

select 
  day, 
  period_type, 
  event_location, 
  count(distinct event_uuid) as number_events
from base t, 
unnest([
  struct('day' as period_type, date_trunc(event_datetime, day) as day),
  struct('week', date_trunc(event_datetime, week)),
  struct('month', date_trunc(event_datetime, month))
]) 
group by day, period_type, event_location