postgresql daysdiff在按月份分组的两个日期之间

我有一个带有日期列（开始日期、结束日期）的表，我想计算这些日期之间的差异，并按月份分组

我可以在几天内得到datediff，但我不知道如何在一个月内将其分组，有什么建议吗

Table:
id       Start_date   End_date      days      
1234     2014-06-03   2014-07-05     32
12345    2014-02-02   2014-05-10     97

Expected results:
month  diff_days
2      26
3      30
4      31
5      10
6      27    
7      5

---

我认为你们的预期产量有点低。你可能想再检查一遍

我自己使用日历表，但这个查询使用CTE和日期算法。避免硬编码日期“2014-01-01”和365天的间隔很简单，但这会使查询更难阅读，所以我直接使用了这些值

with your_data as (
  select date '2014-06-03' as start_date, date '2014-07-05' as end_date union all
  select '2014-02-02', '2014-05-10'
), calendar as (
  select date '2014-01-01' + (n || ' days')::interval calendar_date
  from generate_series(0, 365) n
)
select extract (month from calendar_date) calendar_month, count(*) from calendar
inner join your_data on calendar.calendar_date between start_date and end_date
group by calendar_month
order by calendar_month;

---

谢谢你，它成功了。关于不同年份的分组，我有一个很好的观点，我目前正在使用一个case语句只显示当前年份的数据（日期为“2014-01-01”+（n | | |“days”）：：interval<“2014-12-31”然后date“2014-01-01”+（n | |“days”）：：interval END）日历日期。这几乎仅限于今年，我确实有截止到2015年的日期，知道如何在2014年的几个月里提取和分组这些数据吗？太棒了。非常感谢你，迈克！！ calendar_month count -- 2 27 3 31 4 30 5 10 6 28 7 5

with your_data as (
  select date '2014-06-03' as start_date, date '2014-07-05' as end_date union all
  select '2014-02-02', '2014-05-10' 
), calendar as (
  select date '2014-01-01' + (n || ' days')::interval calendar_date
  from generate_series(0, 700) n
)
select extract (year from calendar_date) calendar_year, extract (month from calendar_date) calendar_month, count(*) from calendar
inner join your_data on calendar.calendar_date between start_date and end_date
where calendar_date between '2014-01-01' and '2014-12-31'
group by calendar_year, calendar_month
order by calendar_year, calendar_month;

with min_max as (
    select min(start_date) as start_date, max(end_date) as end_date
    from t
), g as (
    select daterange(d::date, (d + interval '1 month')::date, '[)') as r
    from generate_series(
        (select date_trunc('month', start_date) from min_max),
        (select end_date from min_max),
        '1 month'
    ) g(d)
)
select *
from (
    select
        to_char(lower(r), 'YYYY Mon') as "Month",
        sum(upper(r) - lower(r)) as days
    from (
        select t.r * g.r as r
        from
            (
                select daterange(start_date, end_date, '[]') as r
                from t
            ) t
            inner join
            g on t.r && g.r
    ) s
    group by 1
) s
order by to_timestamp("Month", 'YYYY Mon')
;
  Month   | days 
----------+------
 2014 Feb |   27
 2014 Mar |   31
 2014 Apr |   30
 2014 May |   10
 2014 Jun |   28
 2014 Jul |    5