数据库：SQL Server 2008 R2
表格结构：
location, date, temperature
NY 2011-12-06 21:07:00 -05:00 20
NY 2011-12-06 21:08:00 -05:00 21
NY 2011-12-06 21:09:00 -05:00 22
NY 2011-12-06 21:10:00 -05:00 23
NY 2011-12-06 21:11:00 -05:00 24 <- Minute breaks here
NY 2011-12-06 21:22:00 -05:00 27
NY 2011-12-06 21:23:00 -05:00 25
NY 2011-12-06 21:24:00 -05:00 26
NY 2011-12-06 21:25:00 -05:00 25
NY 2011-12-06 21:26:00 -05:00 26
NY 2011-12-06 21:27:00 -05:00 24 <- Minute breaks here(NY ends)
MA 2011-12-06 21:07:00 -05:00 21
MA 2011-12-06 21:08:00 -05:00 22
MA 2011-12-06 21:09:00 -05:00 24
MA 2011-12-06 21:10:00 -05:00 23
MA 2011-12-06 21:11:00 -05:00 22 <- Minute breaks here
MA 2011-12-06 21:22:00 -05:00 22
MA 2011-12-06 21:23:00 -05:00 25
MA 2011-12-06 21:24:00 -05:00 26
MA 2011-12-06 21:25:00 -05:00 24
MA 2011-12-06 21:26:00 -05:00 25
MA 2011-12-06 21:27:00 -05:00 29
要求：该表还有一个名为running_average_temp的列。计算日期连续分钟的临时运行平均值的最佳方法是什么？ （即，每个位置的完整分钟读数都是一组数据，需要为此组中的每一行计算运行平均值）该表有更多位置。
（POST要求：这个表每小时都会得到它的输入。进入的新行集可以是现有行的连续几分钟，也可以是一组新的读数。什么是最好的计算方法。每小时进入的新集合的平均值。）
答案 0 :(得分：0)
这是一个答案，将一些边缘情况添加到数据集中。
DECLARE @temps TABLE
(
location varchar(2) NOT NULL,
date datetime NOT NULL,
temperature tinyint NOT NULL
)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:07:00',20)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:08:00',21)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:09:00',22)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:10:00',23)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:11:00',24) --<- Minute breaks here
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:22:00',27)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:23:00',25)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:24:00',26)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:25:00',25)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:26:00',26)
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 21:27:00',24) --<- Minute breaks here
INSERT INTO @temps (location, date, temperature) VALUES ('NY', '2011-12-06 22:00:00',28) --<- Minute breaks here
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:07:00',21)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:08:00',22)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:09:00',24)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:10:00',23)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:11:00',22) --<- Minute breaks here
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:22:00',22)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:23:00',25)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:24:00',26)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:25:00',24)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:26:00',25)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 21:27:00',29)
INSERT INTO @temps (location, date, temperature) VALUES ('MA', '2011-12-06 22:00:00',32)--<- Minute breaks here
;WITH TempSets (RowNumber, location, date, temperature, nextminutetemperature, previousminutetemperature)
AS
(
SELECT
ROW_NUMBER() OVER (ORDER BY T.location ASC, T.date ASC) AS RowNumber,
T.location,
T.date,
T.temperature,
T1.temperature AS nextminutetemperature,
T2.temperature AS previousminutetemperature
FROM
@temps T
LEFT JOIN @temps T1 ON
T1.location = T.location
AND T1.date = DATEADD(minute, +1, T.date)
LEFT JOIN @temps T2 ON
T2.location = T.location
AND T2.date = DATEADD(minute, -1, T.date)
)
SELECT
Result.location,
MIN(Result.date) AS starttime,
MAX(Result.date) AS endtime,
COUNT(Result.groupidentifier) AS numberofreadings,
AVG(Result.temperature) AS averagetemperature
FROM
(
SELECT
(
CASE
WHEN
TempSets.previousminutetemperature IS NULL
AND TempSets.nextminutetemperature IS NULL
THEN TempSets.rownumber
ELSE
(
SELECT
MIN(GroupNumber.rownumber)
FROM
TempSets AS GroupNumber
WHERE
GroupNumber.location = TempSets.location
AND GroupNumber.rownumber >= TempSets.rownumber
AND GroupNumber.nextminutetemperature IS NULL
)
END
) AS groupidentifier,
TempSets.rownumber,
TempSets.location,
TempSets.date,
TempSets.temperature,
TempSets.nextminutetemperature,
TempSets.previousminutetemperature
FROM
TempSets
) AS Result
GROUP BY
Result.groupidentifier,
Result.location
ORDER BY
Result.location ASC,
MIN(Result.date) ASC
结果：
location starttime endtime numberofreadings averagetemperature
-------- ----------------------- ----------------------- ---------------- ------------------
MA 2011-12-06 21:07:00.000 2011-12-06 21:11:00.000 5 22
MA 2011-12-06 21:22:00.000 2011-12-06 21:27:00.000 6 25
MA 2011-12-06 22:00:00.000 2011-12-06 22:00:00.000 1 32
NY 2011-12-06 21:07:00.000 2011-12-06 21:11:00.000 5 22
NY 2011-12-06 21:22:00.000 2011-12-06 21:27:00.000 6 25
NY 2011-12-06 22:00:00.000 2011-12-06 22:00:00.000 1 28