sql - 每周 Postgres 条目，每周

Question

我想返回每个日历周的每周条目数。我当前的代码:

SELECT COUNT(*) AS count, date_trunc('week', occured_on) AS week
from incidents
GROUP BY date_trunc('week', occured_on)
ORDER BY date_trunc('week', occured_on);

返回:

count  |        week         
-------+---------------------
     1 | 2009-09-28 00:00:00
     2 | 2009-10-19 00:00:00
     6 | 2009-10-26 00:00:00
     3 | 2009-11-02 00:00:00
     6 | 2009-11-09 00:00:00
    22 | 2009-11-16 00:00:00

跳过没有发生事故的一周。我如何获得该周的 0 计数，显示每个日历周的条目总数，而不是每周发生事件？

Answer 1

您可以通过生成周系列然后在聚合之前使用 left join 来完成此操作。下面使用 CTE 生成系列。这不是必需的，但我认为它显示了正在使用的逻辑:

with dates as (
      select min(date_trunc('week', occured_on)) as startw,
             max(date_trunc('week', occured_on)) as endw
      from incidents
     ),
     weeks as (
      select generate_series(startw, endw, '7 days') as week
      from dates
     )
select w.week, count(i.occured_on)
from weeks w left outer join
     incidents i
     on date_trunc('week', i.occured_on) = w.week
group by w.week;

SQL Fiddle 是 here .