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Difference between two date/times and flag each hour in between


Difference between two date/times and flag each hour in between

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cs_source
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I'm stumped!

I have a request where i would like to get the start date/time and end date/time and flag (with an int) which hours (24 hour clock) have values between the two dates. Example car comes into service on 2013-12-25 at 0800 and leaves 2013-12-25 at 1400 the difference is 6 hours and i need my table to show

Column: Hour_6 Value: 0
Column: Hour_7 Value: 0
Column: Hour_8 Value: 1
Column: Hour_9 Value: 1
Column: Hour_10 Value: 1
Column: Hour_11 Value: 1
Column: Hour_12 Value: 1
Column: Hour_13 Value: 1
Column: Hour_14 Value: 0

As i'm working away at it i'm trying to figure out how i could use a Time Dimension table for this but dont really see much.

So far i have the difference between the two times in hours (hour_diff) and the start hour (min_hour) so i would like to do something where i update the first hour (min_hour) and update columns based on the numbers of hours (hour_diff)

Advice on how i can go about this would be greatly appreciated ! Thank you and Happy New Years!
CodeMuddler
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Can you include table structure for your data describing when cars begin and end their service period? How those tables are laid out is going to have a pretty big impact on how best to get the result set you're after.

Edit: See this article for how best to frame your question.

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Nevyn
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If you've already got a time dimension it should be be too hard from there.

First, a question, do you include an hour if the start is during that hour (same for end)?

For example, if it comes in at 0841, should the 8 oclock hour get a 1? If it leaves at 0901, should the 9 oclock hour get a 1?

What you are basically going to do is join to your time dimension based on the two dates, grouping based on hours. But the particulars come down to your table definitions and your requirements (hence the question above)
cs_source
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Thanks for the replies i did figure it out and used my time dimension, below is the code for those wondering:

select distinct t.visit_date,t.car_id,t.car_color,d.hour_of_day_24
from TABLE t
inner join DIMENSION d
on d.string_representation_24 between t.car_start_date and t.car_end_date

the answer to the question above is yes both 0800 get a 1 and 0900 gets 1 regardless if the car was there for an hour. I am trying to capture volume by hour. That is only half of the request the next half will be challenging as well.
cs_source
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well i found a bug with the code posted and that is it doesn't include records that stay longer than a day...
so back to square one.
samalex
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You didn't give much to work with, but here's an example of how I'd do this given your dimTime table is similar to ones I usually use. Also I'm using the [Whatever] table to denote occurrences during specific times:


-- Setup Whatever Table
CREATE TABLE Whatever (TimeDateKey DATETIME, Occurrence INTEGER);
INSERT INTO Whatever (TimeDateKey, Occurrence) VALUES
   ('2013-12-25 09:11',1),
   ('2013-12-25 10:15',1),
   ('2013-12-25 10:44',1),
   ('2013-12-25 11:43',1)

-- Setup Time Dimention
DECLARE @TimeLoop TIME = '00:01'
CREATE TABLE dimTime (TimeKey TIME, TimeHour INTEGER, TimeMinute INTEGER, PartOfDay CHAR(2))
INSERT INTO dimTime (TimeKey, TimeHour, TimeMInute, PartofDay) VALUES ('00:00',0,0,'AM')
WHILE @TimeLoop <> '00:00'
BEGIN
INSERT INTO dimTime (TimeKey, TimeHour, TimeMInute, PartofDay) VALUES (
   @TimeLoop,
   DATEPART(HOUR,@TimeLoop),
   DATEPART(Minute,@TimeLoop),
   CASE WHEN @TimeLoop < '12:00' THEN 'AM' ELSE 'PM' END)

   SET @TimeLoop = DATEADD(Minute,1,@TimeLoop)
END

-- Query
DECLARE   @StartTime DATETIME = '2013-12-25 08:00',
      @EndTime DATETIME = '2013-12-25 14:00';

WITH OutputTable ([Hours],[Occurrences]) as (
   SELECT   'Hour_' + RIGHT('0' + CONVERT(VARCHAR(2),t.TimeHour),2) AS [Hours],
         COUNT(w.Occurrence) as [Occurrences]
   FROM   dimTime t
         LEFT OUTER JOIN Whatever w ON
            DATEPART(hour,w.TimeDateKey) = t.TimeHour
   WHERE   t.TimeHour BETWEEN DATEPART(HOUR,@StartTime) AND DATEPART(HOUR,@EndTime) AND
         t.TimeMinute = 0
   GROUP BY 'Hour_' + RIGHT('0' + CONVERT(VARCHAR(2),t.TimeHour),2))
SELECT   [Hours],
      CASE WHEN [Occurrences] = 0 THEN 0 ELSE 1 END AS [Occurrences]
FROM   OutputTable

-- Cleanup
DROP TABLE Whatever
DROP TABLE dimTime





The output will be this:
Hours Occurrences
Hour_08 0
Hour_09   1
Hour_10   1
Hour_11   1
Hour_12   0
Hour_13   0
Hour_14   0
cs_source
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Hi salamex,

Thank you, this query is very similar to my first query and it works great if the car is in "service/shop" on the same day, the problem i ran into after doing some validation is that it excludes cars that span more than one day.

That is because the "between" join doesn't work example:

same day : 08:00 - 13:00 (8,9,10,11,12,13)
different day: 21:00 - 03:00 (null)

i think i'll just need to do 2 queries but still working it out.
dwain.c
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I'm not sure if this is exactly what you want but you might want to look at it and see if it gives you some ideas.


WITH SampleData (ID, SDT, EDT) AS
(
SELECT 1, CAST('2013-12-25 08:00' AS DATETIME), CAST('2013-12-25 13:00' AS DATETIME)
UNION ALL SELECT 2, CAST('2013-12-25 10:00' AS DATETIME), CAST('2013-12-26 12:00' AS DATETIME)
),
Tally (n) AS
(
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM (VALUES (0),(0),(0),(0),(0),(0)) a (n)
CROSS JOIN (VALUES (0),(0),(0),(0)) b (n)
)
SELECT HourOfDay=n, CountOfCars=SUM(flag)
FROM (
SELECT n
,flag=CASE WHEN std = d AND ed = d AND n BETWEEN DATEPART(hour, SDT) AND DATEPART(hour, EDT) THEN 1
WHEN std = d AND ed <> d AND DATEPART(hour, SDT) >= n THEN 1
WHEN ed = d AND std <> d AND DATEPART(hour, EDT) <= n THEN 1
WHEN d NOT IN (std, ed) THEN 1
ELSE 0
END
FROM SampleData a
CROSS APPLY
(
SELECT TOP (1+DATEDIFF(day, SDT, EDT))
d=DATEADD(day, DATEDIFF(day, 0, SDT), n-1)
,std=DATEADD(day, DATEDIFF(day, 0, SDT), 0)
,ed=DATEADD(day, DATEDIFF(day, 0, EDT), 0)
FROM Tally
) b
CROSS APPLY Tally c
WHERE n IN (6,7,8,9,10,11,12,13,14)
) a
GROUP BY n;




If your car can be in the shop for more than 24 days, you'll need a bigger Tally table.


My mantra: No loops! No CURSORs! No RBAR! Hoo-uh!

My thought question: Have you ever been told that your query runs too fast?

My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.


Need to UNPIVOT? Why not CROSS APPLY VALUES instead?
Since random numbers are too important to be left to chance, let's generate some!
Learn to understand recursive CTEs by example.
Splitting strings based on patterns can be fast!
My temporal SQL musings: Calendar Tables, an Easter SQL, Time Slots and Self-maintaining, Contiguous Effective Dates in Temporal Tables
ChrisM@Work
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cs_source (1/2/2014)
Hi salamex,

Thank you, this query is very similar to my first query and it works great if the car is in "service/shop" on the same day, the problem i ran into after doing some validation is that it excludes cars that span more than one day.

That is because the "between" join doesn't work example:

same day : 08:00 - 13:00 (8,9,10,11,12,13)
different day: 21:00 - 03:00 (null)

i think i'll just need to do 2 queries but still working it out.


A little sample data would go a long way.

“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden
Exploring Recursive CTEs by Example Dwain Camps
cs_source
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Thank you dwain.c, i'm working through the query now to under stand it (pretty complicated Smile

hi Chris.m below is the sample data as well as my expected output (sorry i should have provided this earlier)

CREATE TABLE [dbo].[sampleA](
   [visit_date] [date] NULL,
   [enter_datetime] [datetime] NULL,
   [depart_datetime] [datetime] NULL,
   [vin] [int] NULL,
   [make] [char](10) NULL
) ON [PRIMARY]


INSERT INTO [sampleA]
([visit_date]
,[enter_datetime]
,[depart_datetime]
,[vin]
,[make])
VALUES
('2011-01-01','2011-01-01 23:00','2011-01-02 1:35','222','vw'),
('2012-01-08','2012-01-08 22:30','2012-01-11 17:01','333','honda'),
    ('2013-12-25','2013-12-25 0:10','2013-12-25 2:25','111','ford')
GO

--DROP TABLE SampleA

Expected output (i insert these into another table for further manipulationSmile

visit_date VIN make    Hour_in_service
12/25/2013   111   ford    0
12/25/2013   111   ford    1
12/25/2013   111   ford    2
1/1/2011   222   vw    23
1/2/2011   222   vw    0
1/2/2011   222   vw    1
1/8/2012   333   honda   22
1/8/2012   333   honda   23
1/9/2012   333   honda   0
1/9/2012   333   honda   1
1/9/2012   333   honda   2
1/9/2012   333   honda   3
1/9/2012   333   honda   4
1/9/2012   333   honda   5
1/9/2012   333   honda   6
1/9/2012   333   honda   7
1/9/2012   333   honda   8
1/9/2012   333   honda   9
1/9/2012   333   honda   10
1/9/2012   333   honda   11
1/9/2012   333   honda   12
1/9/2012   333   honda   13
1/9/2012   333   honda   14
1/9/2012   333   honda   15
1/9/2012   333   honda   16
1/9/2012   333   honda   17
1/9/2012   333   honda   18
1/9/2012   333   honda   19
1/9/2012   333   honda   20
1/9/2012   333   honda   21
1/9/2012   333   honda   22
1/9/2012   333   honda   23
1/10/2012   333   honda   0
1/10/2012   333   honda   1
1/10/2012   333   honda   2
1/10/2012   333   honda   3
1/10/2012   333   honda   4
1/10/2012   333   honda   5
1/10/2012   333   honda   6
1/10/2012   333   honda   7
1/10/2012   333   honda   8
1/10/2012   333   honda   9
1/10/2012   333   honda   10
1/10/2012   333   honda   11
1/10/2012   333   honda   12
1/10/2012   333   honda   13
1/10/2012   333   honda   14
1/10/2012   333   honda   15
1/10/2012   333   honda   16
1/10/2012   333   honda   17
1/10/2012   333   honda   18
1/10/2012   333   honda   19
1/10/2012   333   honda   20
1/10/2012   333   honda   21
1/10/2012   333   honda   22
1/10/2012   333   honda   23
1/11/2012   333   honda   0
1/11/2012   333   honda   1
1/11/2012   333   honda   2
1/11/2012   333   honda   3
1/11/2012   333   honda   4
1/11/2012   333   honda   5
1/11/2012   333   honda   6
1/11/2012   333   honda   7
1/11/2012   333   honda   8
1/11/2012   333   honda   9
1/11/2012   333   honda   10
1/11/2012   333   honda   11
1/11/2012   333   honda   12
1/11/2012   333   honda   14
1/11/2012   333   honda   15
1/11/2012   333   honda   16
1/11/2012   333   honda   17
Go


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