Recursive data but increasing date by one day

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Recursive data but increasing date by one day

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steve.tarry SSC Enthusiast Points: 132 More actions · Answer 1

Or something like this

DECLARE @PatientDATE = '2015-01-04';

DECLARE @Discharged DATE = '2015-01-19';

DECLARE @STARTDATEDATE = getdate();

DECLARE @ENDDATEDATE = getdate()+7;

WITH DateCTE AS (

SELECT@startdate AS myDate -- add half the recursive to the day dot SQL date 1900-01-01

,datediff(d, @patient, @startdate) as days

UNION ALL

SELECTDATEADD(Day,1,myDate) myDate1

, 0

FROMDateCTE

WHEREDATEADD(Day,1,myDate) <= @Enddate -- loop through the max recursion

)

Select d.*

, @Patient

, @Discharged

, datediff(d, @Patient, Case When myDate < @Discharged Then myDate else @Discharged end

) DaysInHospital

, datediff(d, @Patient, myDate) DaysInHospital

, case when @discharged > @startdate then

datediff(d, @Patient, myDate) else 0

end Inhospital

From DateCTE d

OPTION (MAXRECURSION 32767)

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 2

steve.tarry (1/21/2015)
Recursive Date
DECLARE @STARTDATE DATE = getdate();
DECLARE @ENDDATE DATE = '2015-03-21';
WITH DateCTE AS (
SELECT@startdate AS myDate -- can be parameter supplied
UNION ALL
SELECTDATEADD(Day,1,myDate) myDate1
FROMDateCTE
WHEREDATEADD(Day,1,myDate) <= @Enddate -- set the to date
)
Select * From DateCTE
OPTION (MAXRECURSION 32767)

rCTE is an expensive way to generate dates. Try this method - it's a kinda standard around here because it's a) cheap and b) easy to code.

Check BOL for OPTION (MAXRECURSION 0)

^{“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

steve.tarry SSC Enthusiast Points: 132 More actions · Answer 3

Thanks for the piece of code. Very nice. In the grand scheme of things the CTE query executes very quickly but happy to use a better solution.

Great stuff.

Have a good day.

Jeff Moden SSC Guru Points: 1000539 More actions · Answer 4

steve.tarry (1/21/2015)
Thanks for the piece of code. Very nice. In the grand scheme of things the CTE query executes very quickly but happy to use a better solution.
Great stuff.
Have a good day.

CTEs are great. It's the recursive ones that increment that are both a performance and resource usage problem.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.
"Change is inevitable... change for the better is not".

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Intro to Tally Tables and Functions