我写了一个正在进行X聚合的查询。
它从本周的周一开始到当天。
select
extract(dow from time_sent) days
, count(id)
from messages
where time_sent between date_trunc('week', now()) and now()
group by days
order by days;
我想知道如何在星期一没有添加行时为星期一设置默认值。
即星期一是空的,所以我得到了这个:
[ anonymous { day: 2, count: '1' },
anonymous { day: 3, count: '1' },
anonymous { day: 4, count: '1' },
anonymous { day: 5, count: '1' },
anonymous { day: 6, count: '1' } ]
预期结果:
[ anonymous { day: 1, count: '0' },
anonymous { day: 2, count: '1' },
anonymous { day: 3, count: '1' },
anonymous { day: 4, count: '1' },
anonymous { day: 5, count: '1' },
anonymous { day: 6, count: '1' } ]
编辑:添加表结构和示例输出。
id | time_sent
1 | 2018-01-13 15:26:21.443828+08
2 | 2018-01-12 15:26:21.44755+08
3 | 2018-01-11 15:26:21.459208+08
4 | 2018-01-10 15:26:21.440648+08
5 | 2018-01-09 15:26:21.457262+08
查询#1:
select
coalesce(extract(dow from time_sent), d) days
, count(message_batch_id)
from generate_series(0,6) d
left join messages
on d = extract(dow from time_sent)
where time_sent between date_trunc('week', now()) and now()
group by days
order by days;
查询#1输出:
days | count
2 | 1
3 | 1
4 | 1
5 | 1
6 | 1
编辑:我需要澄清messages
表周一没有任何行输入。
编辑:
出于某种原因,此查询返回我想要的行结构:
select
extract(dow from d.*) days,
count(id)
from GENERATE_SERIES(DATE_TRUNC('WEEK', NOW()), NOW(), '1
DAY'::INTERVAL) d
left outer join messages m
on m.time_sent::DATE = d
group by days
order by days;
尝试:
select
coalesce(extract(dow from time_sent),d) days
, count(id)
from generate_series(0,6) d
left outer join messages on d = extract(dow from time_sent)
where time_sent between date_trunc('week', now()) and now()
group by days
order by days;
(没试过)
谓词不能扩展行。你必须使用GENERATE_SERIES
生成日期并与messages
一起加入:
SELECT extract(dow from time_sent) days, coalesce(count(id), 0)
FROM GENERATE_SERIES(DATE_TRUNC('WEEK', NOW()), NOW(), '1 DAY'::INTERVAL) d
LEFT JOIN messages ON time_sent::DATE = d
GROUP BY days
ORDER BY days;
由于某种原因,这会返回我期待的结果。即
返回一周中某一天的行(即使该特定日期没有行条目)
select
extract(dow from d.*) days,
count(id)
from GENERATE_SERIES(DATE_TRUNC('WEEK', NOW()), NOW(), '1
DAY'::INTERVAL) d
left outer join messages m
on m.time_sent::DATE = d
group by days
order by days;