如何在 PostgreSQL 中获取星期开始和结束日期字符串? [英] How to get week start and end date string in PostgreSQL?

问题描述

我正在使用 PostgreSQL 8.3.我有一张这样的桌子:

I am using PostgreSQL 8.3. I have a table like this:

id        regist_time        result
-----------------------------------
1     2012-07-09 15:00:08      3
2     2012-07-25 22:24:22      7
4     2012-07-07 22:24:22      8

regist_time的数据类型是timestamp.

我需要找到一个星期的时间间隔(从开始到结束)和 sum(result) 为 num.

I need to find a week time interval(start to end) and sum(result) as num.

我想得到如下结果:

      week                    num    
---------------------------------
7/1/2012-7/7/2012              10
7/8/2012-7/14/2012              5
7/15/2012-7/21/2012             3
7/22/2012-7/28/2012            11

我可以得到今年的周数:

I can get the week number just in this year:

SELECT id,regis_time, EXTRACT(WEEK FROM regis_time) AS regweek
FROM tba

关键部分是

EXTRACT(WEEK FROM regis_time) 

提取函数只能获取今年的周数，如何获取一周内的开始时间到结束时间?

extract function can only get the week number in this year, how can I get start time to end time in one week?

推荐答案

你可以使用date_trunc('week', ...).

例如:

SELECT date_trunc('week', '2012-07-25 22:24:22'::timestamp);
-> 2012-07-23 00:00:00

然后，如果您对开始时间不感兴趣，可以将其转换为日期.

Then, you can convert this into a date, if you're not interested in a start time.

也获取结束日期:

SELECT    date_trunc('week', '2012-07-25 22:24:22'::timestamp)::date
   || ' '
   || (date_trunc('week', '2012-07-25 22:24:22'::timestamp)+ '6 days'::interval)::date;

-> 2012-07-23 2012-07-29

(我这里使用了默认格式，你当然可以修改为使用 MM/DD/YYYY.)

(I've used the default formatting here, you can of course adapt this to use MM/DD/YYYY.)

请注意，如果您想比较时间戳，而不是使用 (date_trunc('week', ...) + '6 days'::interval，您可能需要添加整整一周，并在一周结束时使用严格的比较.

Note that, if you want to make comparisons on timestamps, instead of using (date_trunc('week', ...) + '6 days'::interval, you might want to add an entire week and use a strict comparison for the end of the week.

这将排除一周最后一天的 y 时间戳(因为截止时间是当天的午夜).

This will exclude y timestamps on the last day of the week (since the cut-off time is midnight on the day).

    date_trunc('week', x)::date <= y::timestamp
AND y::timestamp <= (date_trunc('week', x) + '6 days'::interval)::date

这将包括他们:

    date_trunc('week', x)::date <= y::timestamp
AND y::timestamp < (date_trunc('week', x) + '1 week'::interval)

(在极少数情况下，您不能直接在 y 上使用 date_trunc.)

(That's in the rare cases when you can't use date_trunc on y directly.)

如果您的一周从星期日开始，请将 date_trunc('week', x)::date 替换为 date_trunc('week', x + '1 day'::interval)::date - '1 day'::interval 应该可以工作.

If your week starts on a Sunday, replacing date_trunc('week', x)::date with date_trunc('week', x + '1 day'::interval)::date - '1 day'::interval should work.

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