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Logic to break period of time by month Expand / Collapse
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Posted Wednesday, August 21, 2013 10:04 PM
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Hi,
Can anybody give me and idea if it's possible, I need to check the following table and do some logic counting period of time but withing each of month, so let say for id=303 with period = 45, I'll get 3 records ,etc:
    303  6/27/13      8/11/13      45
||
\/

1 303 6/27/13 6/30/13 3
2 303 7/01/13 7/31/13 31
3 303 8/01/13 8/11/13 11


Is there any date function to do this in TSQL?
my sample data
with ttt as (
select 123 Id, DATEADD(d,-10,getdate()) fromDD, DATEADD(d,-3,getdate()) toDD,
datediff(d, DATEADD(d,-10,getdate()), DATEADD(d,-3,getdate())) period ,1000 prodID union
select 202 Id, DATEADD(d,-25,getdate()) fromDD, DATEADD(d,-17,getdate()) toDD,
datediff(d, DATEADD(d,-25,getdate()), DATEADD(d,-17,getdate())) period ,2000 prodID union
select 303 Id, DATEADD(d,-55,getdate()) fromDD, DATEADD(d,-10,getdate()) toDD,
datediff(d, DATEADD(d,-55,getdate()), DATEADD(d,-10,getdate())) period ,3000 prodID
)

select * from ttt

Thanks Mario
Post #1487039
Posted Wednesday, August 21, 2013 11:00 PM
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If you just want the difference between the dates in the two columns
datediff(mm,col1,col2) + 1 to include the first month

eg select datediff(mm,'6/27/13','8/11/13') +1

Cheers

Jamie


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We shall go always, a little further.
Post #1487048
Posted Wednesday, August 21, 2013 11:41 PM


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I believe you can do it something like this.

with ttt as (
select 123 Id, DATEADD(d,-10,getdate()) fromDD, DATEADD(d,-3,getdate()) toDD,
datediff(d, DATEADD(d,-10,getdate()), DATEADD(d,-3,getdate())) period ,1000 prodID union
select 202 Id, DATEADD(d,-25,getdate()) fromDD, DATEADD(d,-17,getdate()) toDD,
datediff(d, DATEADD(d,-25,getdate()), DATEADD(d,-17,getdate())) period ,2000 prodID union
select 303 Id, DATEADD(d,-55,getdate()) fromDD, DATEADD(d,-10,getdate()) toDD,
datediff(d, DATEADD(d,-55,getdate()), DATEADD(d,-10,getdate())) period ,3000 prodID
),
Tally (n) AS (
SELECT number
FROM [master].dbo.spt_values Tally
WHERE [Type] = 'P' AND Number BETWEEN 1 AND 100)
SELECT id, fromDD=MIN(d.DD), toDD=MAX(d.DD), period=COUNT(*), prodID
FROM ttt a
CROSS APPLY (SELECT n FROM Tally WHERE n BETWEEN 1 AND period+1) c
CROSS APPLY (SELECT [month]=DATEPART(month, a.fromDD+n-1),DD=CAST(a.fromDD+n-1 AS DATE)) d
GROUP BY id, prodID, [month]


Note that if you have a period > 100 days, then you'll need a bigger Tally table (examples abound). You can also do this with a Calendar table but that might be a little harder to explain.

Not sure if you really need that last CAST to DATE but you did show your expected results as a DATE and not a DATETIME.



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!
Post #1487064
Posted Thursday, August 22, 2013 1:14 AM
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see familiar fish, Thanks so much Dwain !!!!


Best
M
Post #1487085
Posted Thursday, August 22, 2013 1:45 AM
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Is it possible to assign level (count for how many parts (months) it was broken for each ID),


    
303 6/27/13 8/11/13 45
||
\/
level
1 303 6/27/13 6/30/13 3
2 303 7/01/13 7/31/13 31
3 303 8/01/13 8/11/13 11


Tx again,
Jamie thansk for your post. I got you point, then I can do inpivot.

Best
mario
Post #1487091
Posted Thursday, August 22, 2013 5:24 AM


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mario17 (8/22/2013)
Is it possible to assign level (count for how many parts (months) it was broken for each ID),


    
303 6/27/13 8/11/13 45
||
\/
level
1 303 6/27/13 6/30/13 3
2 303 7/01/13 7/31/13 31
3 303 8/01/13 8/11/13 11


Tx again,
Jamie thansk for your post. I got you point, then I can do inpivot.

Best
mario


Add an outer select to get a ROW_NUMBER():

SELECT Level=ROW_NUMBER() OVER (PARTITION BY id ORDER BY fromdd) 
,id, fromDD, toDD, period, prodID
FROM (
SELECT id, fromDD=MIN(d.DD), toDD=MAX(d.DD), period=COUNT(*), prodID
FROM ttt a
CROSS APPLY (SELECT n FROM Tally WHERE n BETWEEN 1 AND period+1) c
CROSS APPLY (SELECT [month]=DATEPART(month, a.fromDD+n-1),DD=CAST(a.fromDD+n-1 AS DATE)) d
GROUP BY id, prodID, [month]
) a





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!
Post #1487182
Posted Thursday, August 22, 2013 4:36 PM
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You should use your own tally table, either a permanent one or a dynamically generated one. Since the permanent one would be clustered on the tally value, it might give better performance. I'm using a tally CTE in the code below to allow it to be run independently.
[Reason: Aside from the danger that master.dbo.spt_values could be modified, or removed, at any time by MS, you don't want your application needing authority to read from the master db to be able to run!]

You can then do an INNER JOIN to the tally table to expand the months; the tally value conveniently also provides the level -- nice!

;WITH ttt AS (
select 123 Id, DATEADD(d,-10,getdate()) fromDD, DATEADD(d,-3,getdate()) toDD,
datediff(d, DATEADD(d,-10,getdate()), DATEADD(d,-3,getdate())) period ,1000 prodID union all
select 202 Id, DATEADD(d,-25,getdate()) fromDD, DATEADD(d,-17,getdate()) toDD,
datediff(d, DATEADD(d,-25,getdate()), DATEADD(d,-17,getdate())) period ,2000 prodID union all
select 303 Id, DATEADD(d,-55,getdate()) fromDD, DATEADD(d,-10,getdate()) toDD,
datediff(d, DATEADD(d,-55,getdate()), DATEADD(d,-10,getdate())) period ,3000 prodID
),--select * from ttt
cteDigits AS (
SELECT 0 AS digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL
SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
),
cteTally AS (
SELECT [10s].digit * 10 + [1s].digit AS tally
FROM cteDigits [1s]
CROSS JOIN cteDigits [10s]
)
SELECT
t.tally + 1 AS Level,
ttt.Id,
CONVERT(varchar(8),
CASE WHEN t.tally = 0 THEN ttt.fromDD ELSE DATEADD(MONTH, DATEDIFF(MONTH, 0, ttt.fromDD) + t.tally, 0) END
, 1) AS fromDD,
CONVERT(varchar(8),
CASE WHEN DATEDIFF(MONTH, ttt.fromDD, ttt.toDD) = 0 OR DATEADD(MONTH, t.tally, ttt.fromDD) > ttt.toDD THEN ttt.toDD
ELSE DATEADD(DAY, -1, DATEADD(MONTH, DATEDIFF(MONTH, 0, ttt.fromDD) + t.tally + 1, 0)) END
, 1) AS toDD,
DATEDIFF(DAY,
CASE WHEN t.tally = 0 THEN ttt.fromDD ELSE DATEADD(MONTH, DATEDIFF(MONTH, 0, ttt.fromDD) + t.tally, 0) END,
CASE WHEN DATEDIFF(MONTH, ttt.fromDD, ttt.toDD) = 0 OR DATEADD(MONTH, t.tally, ttt.fromDD) > ttt.toDD THEN ttt.toDD
ELSE DATEADD(DAY, -1, DATEADD(MONTH, DATEDIFF(MONTH, 0, ttt.fromDD) + t.tally + 1, 0)) END) + 1 AS Period
FROM ttt
INNER JOIN cteTally t ON
t.tally BETWEEN 0 AND DATEDIFF(MONTH, ttt.fromDD, ttt.toDD)
ORDER BY
Id, Level




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Post #1487577
Posted Friday, August 23, 2013 5:24 PM
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Thanks, Scott
Your code works fine, and much easy to digest ( or learn if you will), amazing.. and thanks again to you and Dwain for sharing this, sure you can read this in books...-)

BTW, Scott
your code produces not correct results if you go beyound 210 days or so, I played with it and found this.
So curious why/where it could happened, tally I think works just fine, it has 100 rows ( for 100 days?), but it still works fine on d,-209 and start breaking on d,-210. (toDD = today = getdate().

You can see looking at toDD for last level, it set to 8/31/13

   select 303 Id, DATEADD(d,-210,getdate()) fromDD,  getdate() toDD,  
datediff(d, DATEADD(d,-210,getdate()), getdate()) period ,3000 prodID

Best to all
M
Post #1488072
Posted Friday, August 23, 2013 5:44 PM
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Dwain,

trying to reverse eng your super code, is this a place to use Cross Apply ONLY, or could be done with Join.
I can't get second Cross Apply

--CROSS APPLY (SELECT n FROM Tally WHERE n BETWEEN 1 AND period+1) c
inner join #Tally on N between 1 and Period+1
CROSS APPLY (SELECT [month]=DATEPART(month, a.fromDD+n-1),DD=CAST(a.fromDD+n-1 AS DATE)) d


Thank again
M
Post #1488075
Posted Friday, August 23, 2013 8:10 PM


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mario17 (8/23/2013)
Dwain,

trying to reverse eng your super code, is this a place to use Cross Apply ONLY, or could be done with Join.
I can't get second Cross Apply

--CROSS APPLY (SELECT n FROM Tally WHERE n BETWEEN 1 AND period+1) c
inner join #Tally on N between 1 and Period+1
CROSS APPLY (SELECT [month]=DATEPART(month, a.fromDD+n-1),DD=CAST(a.fromDD+n-1 AS DATE)) d


Thank again
M


INNER JOIN like that should work assuming your Tally table is in a temporary table. I have a preference for CROSS APPLY.

Are you saying you don't understand what the second CROSS APPLY is doing?

Basically it just does some intermediate calculations. [month] is just the month number which is used later to group the results. DD is the start date + the tally value (-1 to adjust the offset so first n=0).



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!
Post #1488081
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