Question

我们有一个＆＃39;数字＆＃39;在单个值＆＃39; n＆＃39;中保存0-10000值的表。我们有tableX，它有calculated_at datetime和一个术语。我们正在尝试填补tableX在给定日期内没有匹配的漏洞。但是，对于不匹配的...而言，这似乎不会产生NULL或0

select term
     , avg(total::float)
     , date_trunc('day', series.date) as date1
     , date_trunc('day', calculated_at) as date2
from (select 
        (current_timestamp - interval '1 day' * numbers.n)::date as date
      from numbers) as series
full outer join terms
   on series.date = date_trunc('day', calculated_at)
where series.date BETWEEN '2017-07-01' AND '2017-07-30'
AND (term in ('term111') or term is null)
group by term
       , date_trunc('day', series.date)
       , date_trunc('day', calculated_at)
 order by date_trunc('day', series.date) asc

Answer 1

full outer join没问题。问题是过滤器。使用full outer join这些非常棘手。我建议：

select t.term, avg(total::float),
       date_trunc('day', series.date) as date1,
       date_trunc('day', calculated_at) as date2
from (select (current_timestamp - interval '1 day' * numbers.n)::date as date
      from numbers
      where (current_timestamp - interval '1 day' * numbers.n)::date BETWEEN '2017-07-01' AND '2017-07-30'
     ) series full outer join
     (select t.*
      from terms
      where term = 'term111'
     ) t
     on series.date = date_trunc('day', t.calculated_at)
group by t.term, date_trunc('day', series.date), date_trunc('day', calculated_at)
 order by date_trunc('day', series.date) asc;

我的猜测是，left join会做你想要的。我怀疑full outer join是你真正想要的。如果您有疑问，请询问另一个问题并提供样本数据和所需结果。

Redshift FULL OUTER JOIN不输出NULL

1 个答案: