运行 根据 when 语句中的不同日期参数多次查询并合并结果，而不是多次 UNION ALL

Question

我希望从核心 table 中提取和合并类似的聚合，但在 WHEN 语句中定义的日期期间有所不同。这就是我通常这样做的方式：

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

select
  "last_30_days" as period
  , event_location
  , count(distinct event_uuid) as number_events
from base
where event_datetime >= current_date - 30
group by event_location

union all

select
  "last_60_days" as period
  , event_location
  , count(distinct event_uuid) as number_events
from base
where event_datetime >= current_date - 60
group by event_location

union all

select
  "all_time" as period
  , event_location
  , count(distinct event_uuid) as number_events
from base
where event_datetime >= current_date - 10000
group by 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时间段重新运行并联合结果（产生与上面的代码相同的输出）？

Answer 1

考虑以下方法

select 
  period, 
  event_location, 
  count(distinct if(event_datetime >= current_date - days, event_uuid, null)) as number_events
from base, 
unnest([
  struct('last_30_days' as period, 30 as days),
  struct('last_60_days', 60),
  struct('all_time', 10000)
]) 
group by period, event_location