SQL-确定当前活动记录的计数
我有一个包含以下信息的表：SQL-确定当前活动记录的计数,sql,sql-server-2005,Sql,Sql Server 2005,我有一个包含以下信息的表： Conf_Start_Time Part_Start_Time Part_End_Time 如果t介于部分开始时间和部分结束时间之间，则记录在时间t被认为是活动的 我想做的是分析所有记录，以确定给定一天有多少记录处于活动状态。我建议的解决方案是循环一天中的每一分钟（比如从早上6点到晚上9点），并检查当天的每条记录，以确定用户是否在指定的时间t处于活动状态 SQL中是否有解决方案，或者我是否应该继续使用代码解决方案 在代码中，我将把所有记录都放到内存中，循环时间（早上
Conf_Start_Time
Part_Start_Time
Part_End_Time
部分开始时间部分结束时间Record Conf_Start_Time Part_Start_Time Part_End_Time
1. 6/5/2012 13:40:00 6/5/2012 13:41:23 6/5/2012 13:45:27
2. 6/5/2012 13:40:00 6/5/2012 13:40:23 6/5/2012 13:47:29
3. 6/5/2012 13:40:00 6/5/2012 13:42:55 6/5/2012 13:44:17
我需要每天每分钟的数据。然后是这个月的每一天。这种类型的循环甚至可以在SQL中完成吗？如果您希望所有记录都在2012年8月7日处于活动状态，请执行以下操作：
select * from your_table
where '2012-08-07' between Part_Start_Time and Part_End_Time
DECLARE @auxDate datetime
SELECT *
FROM your_table
WHERE @auxDate BETWEEN Part_Start_Time AND Part_End_Time
子句是包容性的，如果您不想包含一些日期，请考虑使用：
DECLARE @auxDate datetime
SELECT *
FROM your_table
WHERE @auxDate >= Part_Start_Time
AND @auxDate <= Part_End_Time
DECLARE@auxDate-datetime
挑选*
从你的桌子上
其中@auxDate>=部分开始时间
和@auxDate下面使用相关子查询来获取所需的数字。这样做的目的是计算累计开始数和累计结束数，直至每次：
with alltimes as
(select t.*
from ((select part_start_time as thetime, 1 as IsStart, 0 as IsEnd
from t
) union all
(select part_end_time, 0 as isStart, 1 as IsEnd
from t
)
) t
)
select t.*,
(cumstarts - cumends) as numactive
from (select alltimes.thetime,
(select sum(isStart)
from allStarts as where as.part_start_time <= alltimes.thetime
) as cumStarts,
(select sum(isEnd)
from allStarts as where as.part_end_time <= alltimes.thetime
) as cumEnds
from alltimes
) t
您需要一个GROUPBY子句：
group by t.thetime
“max”给出了启动优先级（这意味着在相同的时间stampt下，启动被视为首先发生，因此您在那个时间获得了最大的活动）。“Min”将优先考虑端点。如果使用平均值，请记住将其转换为浮点值：
select t.thetime, avg(cumstarts*1.0 - cumends) as avgnumactives
这就是我处理这个问题的方法
我要做的第一件事是创建一个序列表，如下所示。在SQL中，由于各种原因，拥有一个本质上无限（或至少很大）的数字序列是非常有用的。大概是这样的：
create table dbo.sequence
(
seq_no int not null primary key clustered ,
)
declare @v int
set @v = -100000
while @v <= 100000
begin
insert dbo.sequence values ( @v )
set @v = @v+1
end
你到底想退货什么？您能否提供您希望看到的select
语句的示例？样本表数据也很好。@Nicholas我基本上希望看到一个计数数组。对于时间t0=13:40:00到tf=13:43:00的上述信息，我希望获得[0，1，2，3]在特定分钟的需要信息，我可以一次选择一分钟的活动记录。但是我需要遍历一天中的每一分钟。正如最初编写的那样，它将在数据库中拥有每一次。我只是修改了解决方案以获得不同的时间。但是，如果同时有启动和停止，则必须定义“活动”的含义。同时启动和停止将被视为非活动记录。我真的很感激这里的帮助！好东西！事实上，我不是说在同一张唱片上开始和停止。我是说三件事同时开始，两件事同时结束。你会说这是3个活动在那一瞬间（3个开始是“在”结束之前），1个活动（新开始是“在”结束之后），还是2个？我的首选是max（）方法（在结束之前开始），但这取决于您。
create table dbo.sequence
(
seq_no int not null primary key clustered ,
)
declare @v int
set @v = -100000
while @v <= 100000
begin
insert dbo.sequence values ( @v )
set @v = @v+1
end
-----------------------------------------------------------------------------
-- define the range of days in which we are interested
-- it might well be more than 1, but for this example, we'll define the start
-- and end days as the same, so we are interested in just one day.
-----------------------------------------------------------------------------
declare @dtFrom datetime
declare @dtThru datetime
set @dateFrom = '2012-06-01'
set @dateThru = '2012-06-01'
------------------------------------------------------------------------------
-- the next thing in which we are interested in are the boundaries of
-- the time period in which we are interested, and the interval length
-- of each reporting bucket, in minutes.
--
-- For this example, we're interesting in the time period
-- running from 6am through 9pm, such that 6am >= x < 9pm.
--
-- We also need a value defining start-of-day (midnight).
--
-- Setting a datetime value to '' will give you the epoch: 1900-01-01 00:00:00.000
-- Setting a datetime value to just a time-of-day string literal will
-- give you the epoch day at the desired time, so '06:00:00' converts to
-- '1900-01-01 06:00:00'. Crazy, but that's SQL Server.
--
------------------------------------------------------------------------------
declare @start_of_day datetime
declare @timeFrom datetime
declare @timeThru datetime
declare @interval_length_in_minutes int
set @start_of_day = '00:00:00'
set @timeFrom = '06:00:00'
set @timeThru = '21:00:00'
set @interval_length_in_minutes = 15
------------------------------------------------------------------------------
--
-- On to the meat of the matter. This query has three parts to it.
--
-- 1. Generate the set of reporting days, using our sequence table
-- 2. Generate the set of reporting buckets for each day, again, using our sequence table
--
-- The left join of these two virtual tables produces the set of all reporting periods
-- that we will use to match up to the source data that will fill the report.
--
-- 3. Finally, assign each row to 0 or more reporting buckets.
-- A given record has a time range in which it was 'active'.
-- Consequently, it may fall into multiple reporting buckets, and hence,
-- the comparison is a little wonky: A record is assigned to a reporting bucket
-- if both of these are true for the data record:
--
-- * Its active period ended *on or after* the start of the reporting period/bucket.
-- * Its active period began *on or before* the end of the reporting period.
--
-- It take a while to get your head around that, but it works.
--
-- When all that is in place, we use GROUP BY and the aggregate function SUM()
-- to collapse each reporting bucket into a single row and compute the active count.
-- We use SUM() in preference to COUNT() as we want a full report,
-- so we use left joins. Unlike other aggregate functions, COUNT() does not
-- exclude null rows/expressions in its computation.
--
-- There you go. Easy!
--
-----------------------------------------------------------------------------------
select timeFrom = dateadd(minute, times.offset , days.now ) ,
timeThru = dateadd(minute, times.offset + @interval_length_in_minutes , days.now ) ,
N = sum( case when t.id is null then 0 else 1 end ) -- we sum() here rather than count() since we don't want missing rows from dbo.myFunkyTable to increment the count
from ( select now = dateadd(day, seq_no , @dateFrom ) -- get the set of 'interesting' days
from dbo.sequence -- via our sequence table
where seq_no >= 0 --
and seq_no < datediff(day,@dateFrom,@dateThru) --
) days --
left join ( select offset = seq_no -- get the set of time buckets
from dbo.sequence -- each bucket is defined by its offset
where seq_no >= datediff(minute,@start_of_day,@timeFrom) -- as defined in minutes-since-start-of-day
and seq_no < datediff(minute,@start_of_day,@timeThru) -- and is @interval_length_in_minuts long
and 0 = seq_no % @interval_length_in_minutes --
) times
left join dbo.myFunkyTable t on t.Part_StartTime < dateadd(minute, times.offset + @interval_length_in_minutes , days.now )
and t.Part_EndTime >= dateadd(minute, times.offset , days.now )
group by dateadd(minute, times.offset , days.now ) ,
dateadd(minute, times.offset + @interval_length_in_minutes , days.now )
order by 1 , 2