从两个时间戳创建 PostgreSQL `tsrange` [英] Creating a PostgreSQL `tsrange` from two timestamps

问题描述

我正在尝试在 postgresql 查询中创建 tsrange(上周四到上周四)，但出现转换错误.

I am trying to create a tsrange (last Thursday to the previous Thursday) in a postgresql query but I get cast errors.

这就是我到目前为止所得到的(从 this SO question 开始).

This is what I have got so far (starting off from this SO question).

WITH past_week AS (
    SELECT date_trunc('day', NOW() + (s::TEXT || ' day')::INTERVAL)::TIMESTAMP(0) AS day 
    FROM generate_series(-7, 0, 1) AS s)
SELECT (
date_trunc('day', (SELECT day FROM past_week WHERE EXTRACT(DOW FROM day) = '4') - '7 day'::INTERVAL),
date_trunc('day', (SELECT day FROM past_week WHERE EXTRACT(DOW FROM day) = '4')));

这是结果(正确的值，但不是格式，因为它不是范围):

And this is the result (correct value, but not format, since it's not a range):

                      row                      
-----------------------------------------------
 ("2015-10-29 00:00:00","2015-11-05 00:00:00")
(1 row)

现在，有 2 个主要问题困扰着我:

Now, there are 2 main things that bug me:

1. 如果我尝试在查询结束之前添加一个 ::tsrange，解释器会抱怨:

错误:无法将类型记录转换为 tsrange第 6 行:...ROM past_week WHERE EXTRACT(DOW FROM day) = '4')))::tsrange;

ERROR: cannot cast type record to tsrange LINE 6: ...ROM past_week WHERE EXTRACT(DOW FROM day) = '4')))::tsrange;

我很想避免重复，但我对 SQL 的了解并不那么精通.任何改进都非常受欢迎.

I would love to avoid repetition, but I'm not that proficient in SQL to know how. Any improvement is more than welcome.

推荐答案

使用tsrange() 构造函数:

Use tsrange() constructor:

WITH past_week AS (
    SELECT date_trunc('day', NOW() + (s::TEXT || ' day')::INTERVAL)::TIMESTAMP(0) AS day 
    FROM generate_series(-7, 0, 1) AS s)
SELECT tsrange(
    date_trunc('day', 
        (SELECT day FROM past_week 
        WHERE EXTRACT(DOW FROM day) = '4') - '7 day'::INTERVAL),
    date_trunc('day', 
        (SELECT day FROM past_week 
        WHERE EXTRACT(DOW FROM day) = '4')));

                    tsrange                    
-----------------------------------------------
 ["2015-10-29 00:00:00","2015-11-05 00:00:00")
(1 row)

使用 CURRENT_DATE 您的查询可能很简单:

Using CURRENT_DATE your query may be as simple as:

WITH previous_thursday AS (
    SELECT CURRENT_DATE- EXTRACT(DOW FROM CURRENT_DATE)::int+ 4 AS thursday
    )
SELECT tsrange(thursday- '7d'::INTERVAL, thursday)
FROM previous_thursday;

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