sql - 当时间戳开始时间大于时间戳结束时间时查询失败

Question

我有一个基于 CTE 的查询，我在其中检索两个给定时间跨度之间的每小时间隔。我的查询如下:

获取开始和结束日期时间(比如 07-13-2011 00:21:09 和 07-31-2011 21:11:21)获取每小时间隔之间的每小时总查询值(这里是从 00 到21，总共 21 小时，但这是参数化的，取决于我为输入提供的时间)每天。

此查询适用于第一个时间戳的小时数小于第二个时间戳的输入 - 例如第一个时间戳的时间是凌晨 03 点，第二个时间戳的时间是早上 07 点，但是有一个问题。当我想检索 07-13-2011 22:11:43 和 07-25-2011 04:06:04 等输入的查询总数时，我遇到了问题。我需要检索如下查询的总数:

07-13-2011 22:00:00    143 //representing the total amounts of queries 22:11:43 - 22:59:59 interval-
07-13-2011 23:00:00    121 //representing the total amounts of queries in 23:00:00  -23:59:59 interval-
07-14-2011 00:00:00     65 //00:00:00  - 00:59:59 interval
07-14-2011 01:00:00     51 //01:00:00  - 01:59:59 interval...
.
.
.
07-14-2011 04:00:00  22  //query amount for 04:00:00 - 04:06:04 interval

等等。除了我在下面编写的 CTE 查询之外，我还需要做什么？

WITH cal AS (
    SELECT generate_series('2011-02-02 00:00:00'::timestamp
                         , '2012-04-01 05:00:00'::timestamp
                         , '1 hour'::interval) AS stamp
    )
, qqq AS (
    SELECT date_trunc('hour', calltime) AS stamp
    , count(*) AS zcount
    FROM mytable
    WHERE calltime >= '07-13-2011 22:00:00'
    AND calltime <='07-31-2011 04:33:21' 
    AND calltime::time >= '22:00:00' 
    AND calltime::time <= '04:33:21'
    -- this calltime::time part obviously doesn't work due to common sense and logic
    -- edited it to show what I try to mean 
    AND date_part('hour', calltime) >= 0
    AND date_part('hour', calltime) <= 21
    GROUP BY date_trunc('hour', calltime)
    )
SELECT cal.stamp
     , COALESCE (qqq.zcount, 0) AS zcount
FROM cal
LEFT JOIN qqq ON cal.stamp = qqq.stamp
WHERE cal.stamp >= '07-13-2011 22:00:00'
AND cal.stamp<='07-31-2011 04:33:21'
AND date_part('hour', cal.stamp) >= 0
AND date_part('hour', cal.stamp) <= 21
ORDER BY stamp ASC;

Answer 1

考虑这个修改后的版本:

WITH param AS (
   SELECT '2011-07-13 22:11:43'::timestamp AS start -- supply start / stop once
         ,'2011-07-25 04:06:04'::timestamp AS stop
   )
   , cal   AS (
   SELECT generate_series(date_trunc('hour', p.start)
                         ,date_trunc('hour', p.stop + interval '1h')
                         ,interval '1h') AS h
   FROM param p
   )
   , q    AS (
   SELECT date_trunc('hour', calltime) AS h
         ,count(*) AS ct
   FROM   mytable
         ,param p
   WHERE  calltime >= p.start
   AND    calltime <= p.stop
   -- uncomment if you actually want to exclude hours 22 & 23 (?)
   -- AND    extract('hour' FROM calltime) BETWEEN 0 AND 21
   GROUP  BY 1
   )
SELECT cal.h, COALESCE(q.ct, 0) AS ct
FROM   cal
LEFT   JOIN q USING (h)
-- uncomment if you actually want to exclude hours 22 & 23 (?)
-- WHERE  extract('hour' FROM cal.h) BETWEEN 0 AND 21
ORDER  BY 1;

主要变化是立即根据实际时间跨度生成小时数。
删除了几个不需要的条件。
对时间戳使用 ISO 8601 格式(适用于所有语言环境)。

在此 related answer 中查找更多上下文和链接.唯一的区别是:那边是关于正在运行的计数。