我有一张名为data_users的下表
id | created_at
-------+---------------------
20127 | 2015-01-31 04:23:46
21468 | 2015-02-04 07:50:34
21571 | 2015-02-04 08:23:50
20730 | 2015-03-12 10:20:16
19955 | 2015-03-30 07:44:35
20148 | 2015-04-17 13:03:26
21552 | 2015-05-07 19:00:00
20145 | 2015-06-02 03:12:46
21467 | 2015-06-03 13:21:51
21074 | 2015-07-03 19:00:00
我正在尝试查找在Postgres中为动态间隔生成累积总和的查询。
SELECT DISTINCT DATE_TRUNC('DAY', GREATEST(d.date, from)) AS DATE,
SUM(COALESCE(COUNT(u.id), 0)::INT) OVER (ORDER BY DATE)
FROM (SELECT GENERATE_SERIES(MIN(created_at)::DATE, to::DATE, '1 DAY'::INTERVAL) AS date
FROM data_users) d
LEFT OUTER JOIN data_users u ON u.created_at::DATE = d.date::DATE
GROUP BY DATE ORDER BY DATE;
这将返回正确的天数累计总和，但我也想支持其他间隔。
我想支持像MONTH，YEAR，WEEK这样的时间间隔。我需要在查询中更改哪些内容才能支持？
使用案例表达式的想法：
SELECT x.date,
count( case when u.created_at >= x.date and u.created_at < x.date + interval '1' day
then u.id end ) as int_1_day,
count( case when u.created_at >= x.date and u.created_at < x.date + interval '7' day
then u.id end ) as int_1_week,
count( case when u.created_at >= x.date and u.created_at < x.date + interval '1' month
then u.id end ) as int_1_month,
count( case when u.created_at >= x.date and u.created_at < x.date + interval '1' year
then u.id end ) as int_1_year
FROM (
SELECT GENERATE_SERIES(MIN(created_at)::DATE, date '2015-07-31', '1 DAY'::INTERVAL) AS date
FROM data_users
) x
LEFT JOIN data_users u
ON u.created_at BETWEEN x.date and x.date + interval '1' year
GROUP BY x.date
ORDER BY x.date
现场演示：http://sqlfiddle.com/#!17/05e1a/10
注意：连接条件ON u.created_at BETWEEN x.date and x.date + interval '1' year必须使用您需要计算计数的最长间隔，在上面的示例中：+ interval '1' year
让我们看看这次我是否理解。我假设您希望每个间隔都有单独的查询。 （他们可以连在一起。）另外我假设你想要累积整个系列。 （每组可以重新开始积累。）
每日积累可以更简单，仍然给出相同的结果：
\set from_date '''2015-01-01'''
\set to_date '''2015-12-31'''
select distinct
to_char(a.series_date, 'YYYY-MM-DD') as series_date,
count(b.id)
from
(
select
generate_series(:from_date::date, :to_date::date, '1 day'::interval) as series_date
) a
left outer join
data_users b
on date_trunc('day', b.created_at) <= a.series_date
group by
series_date
order by
series_date;
数周：
select distinct
to_char(b.last_day_of_week, 'Day YYYY-MM-DD') as week_ending,
count(c.id)
from
(
select
series_date as last_day_of_week
from
(
select
generate_series(:from_date::date, :to_date::date, '1 day'::interval) as series_date
) a
where
extract('dow' from series_date) = 6
) b
left outer join
data_users c
on date_trunc('day', c.created_at) <= b.last_day_of_week
group by
week_ending
order by
week_ending;
结果：
week_ending | count
----------------------+-------
Saturday 2015-01-03 | 0
Saturday 2015-01-10 | 0
Saturday 2015-01-17 | 0
Saturday 2015-01-24 | 0
Saturday 2015-01-31 | 1
Saturday 2015-02-07 | 3
Saturday 2015-02-14 | 3
Saturday 2015-02-21 | 3
Saturday 2015-02-28 | 3
Saturday 2015-03-07 | 3
Saturday 2015-03-14 | 4
Saturday 2015-03-21 | 4
Saturday 2015-03-28 | 4
Saturday 2015-04-04 | 5
Saturday 2015-04-11 | 5
Saturday 2015-04-18 | 6
Saturday 2015-04-25 | 6
Saturday 2015-05-02 | 6
Saturday 2015-05-09 | 7
Saturday 2015-05-16 | 7
Saturday 2015-05-23 | 7
Saturday 2015-05-30 | 7
Saturday 2015-06-06 | 9
Saturday 2015-06-13 | 9
Saturday 2015-06-20 | 9
Saturday 2015-06-27 | 9
Saturday 2015-07-04 | 10
Saturday 2015-07-11 | 10
Saturday 2015-07-18 | 10
Saturday 2015-07-25 | 10
Saturday 2015-08-01 | 10
Saturday 2015-08-08 | 10
Saturday 2015-08-15 | 10
Saturday 2015-08-22 | 10
Saturday 2015-08-29 | 10
Saturday 2015-09-05 | 10
Saturday 2015-09-12 | 10
Saturday 2015-09-19 | 10
Saturday 2015-09-26 | 10
Saturday 2015-10-03 | 10
Saturday 2015-10-10 | 10
Saturday 2015-10-17 | 10
Saturday 2015-10-24 | 10
Saturday 2015-10-31 | 10
Saturday 2015-11-07 | 10
Saturday 2015-11-14 | 10
Saturday 2015-11-21 | 10
Saturday 2015-11-28 | 10
Saturday 2015-12-05 | 10
Saturday 2015-12-12 | 10
Saturday 2015-12-19 | 10
Saturday 2015-12-26 | 10
(52 rows)
几个月，显示每月最后一天的总数：
select distinct
b.last_day_of_month,
count(c.id)
from
(
select
(extract(year from series_date) || '-' || extract(month from series_date) || '-' || '01')::date +
'1 month'::interval -
'1 day'::interval as last_day_of_month
from
(
select
generate_series(:from_date::date, :to_date::date, '1 month'::interval) as series_date
) a
) b
left outer join
data_users c
on date_trunc('day', c.created_at) <= b.last_day_of_month
group by
last_day_of_month
order by
last_day_of_month;
结果：
last_day_of_month | count
---------------------+-------
2015-01-31 00:00:00 | 1
2015-02-28 00:00:00 | 3
2015-03-31 00:00:00 | 5
2015-04-30 00:00:00 | 6
2015-05-31 00:00:00 | 7
2015-06-30 00:00:00 | 9
2015-07-31 00:00:00 | 10
2015-08-31 00:00:00 | 10
2015-09-30 00:00:00 | 10
2015-10-31 00:00:00 | 10
2015-11-30 00:00:00 | 10
2015-12-31 00:00:00 | 10
(12 rows)
多年来我又增加了3行：
insert into data_users (id, created_at) values (30123, '2016-01-02 03:12:46');
insert into data_users (id, created_at) values (30234, '2016-03-03 13:21:51');
insert into data_users (id, created_at) values (30345, '2016-07-03 19:00:00');
并更改了to_date：
\set to_date '''2017-12-31'''
select distinct
extract('year' from b.last_day_of_year) as year,
count(c.id)
from
(
select
series_date + '1 year'::interval - '1 day'::interval as last_day_of_year
from
(
select
generate_series(:from_date::date, :to_date::date, '1 year'::interval) as series_date
) a
) b
left outer join
data_users c
on date_trunc('day', c.created_at) <= b.last_day_of_year
group by
year
order by
year;
结果：
year | count
------+-------
2015 | 10
2016 | 13
2017 | 13
(3 rows)
我们怎么样？
这听起来太容易了;我错过了什么吗？您可以在PostgreSQL中指定所需的所有间隔，如下所示：
select
'1 day'::interval,
'1 week'::interval,
'1 month'::interval,
'1 year'::interval;
interval | interval | interval | interval
----------+----------+----------+----------
1 day | 7 days | 1 mon | 1 year
(1 row)