在表中的非连续的行之间则DateDiff

Question

我想借此从表1中的时间差的平均值。的值是不连续的，有时被重复的时间价值，所以我需要1）按时间排序，2）丢弃非唯一值，3）执行的时间差（毫秒），然后4）平均所得的时间差值。此外，我想5）限制DATEDIFF操作以选择的时间范围内，如 WHERE _TimeStamp> = '20091220 11：59：56.1' AND _TimeStamp <= _TimeStamp> = '20091220 11：59：56.8'。我很为难如何将所有这些组合起来！

表1：结果 _TimeStamp结果 2009-12-20 11：59：56.0点击 2009-12-20 11：59：56.5点击 2009-12-20 11：59：56.3点击 2009-12-20 11：59：56.4点击 2009-12-20 11：59：56.4点击 2009-12-20 11：59：56.9

Answer 1

下面是一个工程和并不难看：

;WITH Time_CTE AS
(
    SELECT
        MIN(_Timestamp) AS dt,
        ROW_NUMBER() OVER (ORDER BY MIN(_Timestamp)) AS RowNum
    FROM Table1
    GROUP BY _Timestamp
)
SELECT
    t1.dt AS StartDate,
    t2.dt AS EndDate,
    DATEDIFF(MS, t1.dt, t2.dt) AS Elapsed
FROM Time_CTE t1
INNER JOIN Time_CTE t2
ON t2.RowNum = t1.RowNum + 1

会给你从你的例子下面的输出：

StartDate               | EndDate                 | Elapsed
------------------------+-------------------------+--------
2009-12-20 11:59:56.000 | 2009-12-20 11:59:56.300 | 300
2009-12-20 11:59:56.300 | 2009-12-20 11:59:56.400 | 100
2009-12-20 11:59:56.400 | 2009-12-20 11:59:56.500 | 100
2009-12-20 11:59:56.500 | 2009-12-20 11:59:56.900 | 400

编辑：如果你要限制时间范围则WHERE _Timestamp BETWEEN @StartDate AND @EndDate行之前刚刚添加GROUP BY

EDIT2：如果你想平均值，然后更改最终SELECT t1.dt, ...语句：

SELECT AVG(DATEDIFF(MS, t1.dt, t2.dt))
FROM Time_CTE t1 ... (same as above)

Answer 2

步骤1是只选择独特次：

SELECT DISTINCT _TimeStamp FROM table 
    WHERE _TimeStamp >= '20091220 11:59:56.1' AND _TimeStamp <= '20091220 11:59:56.8';

然后，如果你想，说，任何时候都互相比较（不知道你怎么想选择的时间），你可以做喜欢的事，疯狂的：

SELECT t1._TimeStamp, t2._TimeStamp, DATEDIFF(ms,t1._TimeStamp,t2._TimeStamp) FROM 
    (SELECT DISTINCT _TimeStamp FROM table 
        WHERE _TimeStamp >= '20091220 11:59:56.1' AND _TimeStamp <= '20091220 11:59:56.8') AS t1 
    INNER JOIN
    (SELECT DISTINCT _TimeStamp FROM table 
        WHERE _TimeStamp >= '20091220 11:59:56.1' AND _TimeStamp <= '20091220 11:59:56.8') AS t2
WHERE t1._TimeStamp != t2._TimeStamp;

我的语法可能会关闭，因为我从MySQL来了，但类似的事情应该工作。

如果你想要的平均水平，你可以尝试采取上述结果的平均值：

SELECT AVG(DATEDIFF(ms,t1._TimeStamp,t2._TimeStamp)) FROM 
    (SELECT DISTINCT _TimeStamp FROM table 
        WHERE _TimeStamp >= '20091220 11:59:56.1' AND _TimeStamp <= '20091220 11:59:56.8') AS t1 
    INNER JOIN
    (SELECT DISTINCT _TimeStamp FROM table 
        WHERE _TimeStamp >= '20091220 11:59:56.1' AND _TimeStamp <= '20091220 11:59:56.8') AS t2
WHERE t1._TimeStamp != t2._TimeStamp;

还未得到检验，但在理论上，我认为它应该工作。

Answer 3

如果我你想要什么样的假设是正确的，那么，我认为这样做有两种方式。

在直接的方法：

SELECT
    AVG(DATEDIFF(ms, T1.my_time, T2.my_time))
FROM
    My_Table T1
INNER JOIN My_Table T2 ON
    T2.my_time > T1.my_time
WHERE
    NOT EXISTS
    (
        SELECT
            *
        FROM
            My_Table T3
        WHERE
            (T3.my_time > T1.my_time AND T3.my_time < T2.my_time) OR
            (T3.my_time = T1.my_time AND T3.my_pk < T1.my_pk) OR
            (T3.my_time = T2.my_time AND T3.my_pk < T2.my_pk)
    )

棘手的方式：

SELECT
    DATEDIFF(ms, MIN(my_time), MAX(my_time))/(COUNT(DISTINCT my_time) - 1)
FROM
    My_Table

毕竟，平均差异仅仅是总差成你打破它下降分割数分配。

您将需要添加WHERE子句的日期范围内，如果你想通过限制，您将需要通过零在第二个查询占鸿沟的可能性。