选择行数,按PostgreSQL中动态时间间隔的顺序排序

Question

这是我的问题的测试表:

CREATE TABLE document (
    id integer NOT NULL,
    name character varying(120) NOT NULL,
    owner_id bigint DEFAULT 0 NOT NULL,
    doc_type_id smallint DEFAULT 1 NOT NULL,
    archived boolean DEFAULT false NOT NULL,
    insert_date timestamp without time zone DEFAULT now() NOT NULL,
    modify_date timestamp without time zone DEFAULT now() NOT NULL,
    last_writer_id bigint
);

Modify_date确定有人编辑文档的最后时间.

为了进行一些统计,我需要在创建(insert_date)和modify_date之间获得时间.然后要显示一个条形图,我需要得到一个文档的计数,其中这个时间间隔是,例如,0到5天,6天和10天等.所以范围必须在查询中计算我猜.预期的结果(或......的种类)是:

Age                Count
0-5                2
6-10               5
11-15              9
...                ...

当然,年龄可以是0-5 == 0,6-10 == 1的等级.我将准备数据以显示它们.

我发现一个帖子很相似,但我无法将它应用到我的案例中.(选择15分钟窗口的数据 - PostgreSQL)

谢谢你能带给我的任何答案.

编辑1:

范围需要从我从表中获得的最小和最大年龄动态生成.

Answer 1

with cte_ages as (
    select
        extract(day from (modify_date - insert_date))::int as age
    from document
), cte_groups as (
    select
        case when g.age = 1 then 0 else g.age end as gr_start,
        g.age + 4 as gr_end
    from generate_series(1, (select max(age) from cte_ages), 5) as g(age)
)
select
    g.gr_start::text || '-' || g.gr_end::text,
    count(a.age)
from cte_groups as g
    left outer join cte_ages as a on a.age between g.gr_start and g.gr_end
group by g.gr_start, g.gr_end
order by g.gr_start

sql fiddle demo