[大数据]sql计算周月同比

方法一 ：当面对全量表，使用自关联 --笛卡尔积
先看一下笛卡尔积的结果

首先看一下全量表的明细数据

对明细数据进行聚合

select
*
from
(    select count(*) as cnt,app_id,down_date
     from dwd_hispace_down_ds 
     group by app_id,down_date) a
left join
(    select count(*) as cnt,app_id,down_date
     from dwd_hispace_down_ds 
     group by app_id,down_date) b
on a.app_id=b.app_id

select
a.down_date
,a.app_id
,sum(case when a.down_date - b.down_date=7 
 then a.cnt/b.cnt else 0 end) as seven_tb
   ,sum(case when add_months(a.down_date,-1) = b.down_date 
 then a.cnt/b.cnt else 0 end) as month_tb
from
(    select count(*) as cnt,app_id,down_date
     from dwd_hispace_down_ds 
     group by app_id,down_date) a
left join
(    select count(*) as cnt,app_id,down_date
     from dwd_hispace_down_ds 
     group by app_id,down_date) b
on a.app_id=b.app_id
group by 
a.down_date
,a.app_id

方法二：面对每天的增量表，假如是hive大数据的情景下，且数据量特别大，一次只能扫描一天的分区。如要计算20211201当天的周月同比。先看一下所有分区的数据

select
app_id
,nvl(max(cnt)/max(seven_cnt),0)   as seven_tb
,nvl(max(cnt)/max(month_cnt),0) as month_tb
from
(
 select 
  app_id
  ,count(*) as cnt
  ,null as  seven_cnt
  ,null as  month_cnt
 from DWD_HISPACE_DOWN_DM 
 where pt_d=20211201 group by app_id
union all
 select 
  app_id
  ,null as cnt
  ,count(*) as  seven_cnt
  ,null as  month_cnt
 from DWD_HISPACE_DOWN_DM 
 where pt_d=to_char(to_date('20211201','yyyy-mm-dd')-7,'yyyymmdd') group by app_id
union all
 select 
    app_id
    ,null as cnt
    ,null as  seven_cnt
    ,count(*) as  month_cnt
 from DWD_HISPACE_DOWN_DM 
 where pt_d=to_char(add_months(to_date('20211201','yyyy-mm-dd'),-1),'yyyymmdd') group by app_id
 )
 group by app_id

方法三 关联时间维度表

select 
a1.app_id
,sum(a1.cnt)/sum(b1.cnt) as week_tb
 from
(
select 
app_id
,cnt
,b.week_ago
from
(    select count(*) as cnt,app_id,down_date
     from dwd_hispace_down_ds 
     group by app_id,down_date) a
left join dim_time  b
on a.down_date=tO_date(b.today,'yyyymmdd')
) a1
inner join
(
select count(*) as cnt,app_id,down_date
     from dwd_hispace_down_ds 
     group by app_id,down_date 
) b1
on tO_date(a1.week_ago,'yyyymmdd')=b1.down_date
and a1.app_id=b1.app_id
 group by a1.app_id