计算两个日期之间的活动记录数

Question

我正在尝试进行查询以检索给定时间内的活动呼叫数，

我有一个 CALLS 表，其中包含带有 AnsweredTime 和 ReleaseTime 的所有呼叫记录，我需要检索一天中每一秒的活动呼叫数。

所以我做了以下事情：

    SELECT dt,
(SELECT COUNT(Id) FROM Calls WHERE
    AnsweredTimestamp <= dt AND
    ReleasedTimestamp >= dt)
 FROM CALView
WHERE dt >='2011-10-05'
and dt <'2011-10-06'

CalView 是一个包含两个日期之间每一秒的表格

查询返回这个（部分）：

2011-10-05 09:40:00.000 20
2011-10-05 09:40:01.000 20
2011-10-05 09:40:02.000 20
2011-10-05 09:40:03.000 21
2011-10-05 09:40:04.000 21
2011-10-05 09:40:05.000 21
2011-10-05 09:40:06.000 21
2011-10-05 09:40:07.000 21
2011-10-05 09:40:08.000 21
2011-10-05 09:40:09.000 21
2011-10-05 09:40:10.000 20
2011-10-05 09:40:11.000 20
2011-10-05 09:40:12.000 19
2011-10-05 09:40:13.000 19
2011-10-05 09:40:14.000 19
2011-10-05 09:40:15.000 19
2011-10-05 09:40:16.000 19
2011-10-05 09:40:17.000 19
2011-10-05 09:40:18.000 19
2011-10-05 09:40:19.000 19
2011-10-05 09:40:20.000 18
2011-10-05 09:40:21.000 18
2011-10-05 09:40:22.000 18
2011-10-05 09:40:23.000 18
2011-10-05 09:40:24.000 18
2011-10-05 09:40:25.000 18
2011-10-05 09:40:26.000 18
2011-10-05 09:40:27.000 18
2011-10-05 09:40:28.000 18
2011-10-05 09:40:29.000 18
2011-10-05 09:40:30.000 18
2011-10-05 09:40:31.000 18
2011-10-05 09:40:32.000 18
2011-10-05 09:40:33.000 18
2011-10-05 09:40:34.000 18
2011-10-05 09:40:35.000 19
2011-10-05 09:40:36.000 18
2011-10-05 09:40:37.000 18
2011-10-05 09:40:38.000 18
2011-10-05 09:40:39.000 18
2011-10-05 09:40:40.000 18
2011-10-05 09:40:41.000 18
2011-10-05 09:40:42.000 18
2011-10-05 09:40:43.000 18
2011-10-05 09:40:44.000 19
2011-10-05 09:40:45.000 19
2011-10-05 09:40:46.000 19
2011-10-05 09:40:47.000 19
2011-10-05 09:40:48.000 19
2011-10-05 09:40:49.000 19
2011-10-05 09:40:50.000 19
2011-10-05 09:40:51.000 19
2011-10-05 09:40:52.000 19
2011-10-05 09:40:53.000 19
2011-10-05 09:40:54.000 19
2011-10-05 09:40:55.000 19
2011-10-05 09:40:56.000 19
2011-10-05 09:40:57.000 19
2011-10-05 09:40:58.000 20
2011-10-05 09:40:59.000 20
2011-10-05 09:41:00.000 20
2011-10-05 09:41:01.000 20
2011-10-05 09:41:02.000 20
2011-10-05 09:41:03.000 20
2011-10-05 09:41:04.000 20
2011-10-05 09:41:05.000 20
2011-10-05 09:41:06.000 20
2011-10-05 09:41:07.000 20
2011-10-05 09:41:08.000 20
2011-10-05 09:41:09.000 19
2011-10-05 09:41:10.000 19
2011-10-05 09:41:11.000 19
2011-10-05 09:41:12.000 19
2011-10-05 09:41:13.000 19
2011-10-05 09:41:14.000 19
2011-10-05 09:41:15.000 19
2011-10-05 09:41:16.000 20
2011-10-05 09:41:17.000 20
2011-10-05 09:41:18.000 20
2011-10-05 09:41:19.000 20
2011-10-05 09:41:20.000 20
2011-10-05 09:41:21.000 20
2011-10-05 09:41:22.000 20
2011-10-05 09:41:23.000 20
2011-10-05 09:41:24.000 20
2011-10-05 09:41:25.000 20
2011-10-05 09:41:26.000 20
2011-10-05 09:41:27.000 20
2011-10-05 09:41:28.000 20
2011-10-05 09:41:29.000 20
2011-10-05 09:41:30.000 19
2011-10-05 09:41:31.000 19
2011-10-05 09:41:32.000 19
2011-10-05 09:41:33.000 19
2011-10-05 09:41:34.000 20
2011-10-05 09:41:35.000 20
2011-10-05 09:41:36.000 20
2011-10-05 09:41:37.000 19
2011-10-05 09:41:38.000 19
2011-10-05 09:41:39.000 19
2011-10-05 09:41:40.000 19
2011-10-05 09:41:41.000 19
2011-10-05 09:41:42.000 19
2011-10-05 09:41:43.000 19
2011-10-05 09:41:44.000 19
2011-10-05 09:41:45.000 19
2011-10-05 09:41:46.000 18
2011-10-05 09:41:47.000 18
2011-10-05 09:41:48.000 19
2011-10-05 09:41:49.000 20
2011-10-05 09:41:50.000 20
2011-10-05 09:41:51.000 20
2011-10-05 09:41:52.000 20
2011-10-05 09:41:53.000 20

所以我得到了很好的结果，但是查询非常慢，我已经完成了索引，我只是想知道是否还有更多我可以做的事情..

Answer 1

这是一个有趣的笛卡尔坐标，您将在这里创建。

Select dt,count(1)
from calview
left join calls on calls.AnsweredTimestamp <= calview.dt AND
                    calls.ReleasedTimestamp >= calview.dt
WHERE dt >='2011-10-05'
and dt <'2011-10-06'
group by dt

我相信这应该让您在呼叫处于活动状态的每一秒都获得一排......然后这是一个简单的计数。希望我的语法是正确的，我没有 ms sql server 环境来确认。

ETA：使用了左连接，因此任何有 0 次调用的秒数都将显示在此处，计数为空。如果您切换到内连接，则该行将在 1 秒的时间间隔内消失。