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Creating a BookingDate using a random function Expand / Collapse
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Posted Wednesday, February 20, 2013 5:18 AM
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I have an arrival date already in the system and I need to populate the Booking date using a random function, the booking date can be any day on or before the arrival date up to a maximum 90 days previous but it must be random the booking date cannot all be the same date.

I thought I cracked it but was wrong. Can you help?

SELECT ArrivalDate, DATEADD(day, -1 + RAND(checksum(NEWID()))-90
, ArrivalDate) AS BookingDate
FROM Bookings
ORDER BY ArrivalDate

Thanks

Wayne
Post #1422029
Posted Wednesday, February 20, 2013 5:30 AM
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Its alright I have figured it out:

SELECT ArrivalDate, DATEADD(day, -1 + RAND(checksum(NEWID()))*-90
, ArrivalDate) AS BookingDate
FROM Bookings
ORDER BY ArrivalDate
Post #1422032
Posted Wednesday, February 20, 2013 5:46 AM


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wafw1971 (2/20/2013)
Its alright I have figured it out:

...


DwainC already figured it out for you:

SELECT 
ArrivalDate,
BookingDate = DATEADD(day,
-(1 + ABS(checksum(NEWID())) % 90),
ArrivalDate)
FROM Bookings
ORDER BY ArrivalDate



“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
Post #1422039
Posted Wednesday, February 20, 2013 5:59 PM


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ChrisM@Work (2/20/2013)
wafw1971 (2/20/2013)
Its alright I have figured it out:

...


DwainC already figured it out for you:

SELECT 
ArrivalDate,
BookingDate = DATEADD(day,
-(1 + ABS(checksum(NEWID())) % 90),
ArrivalDate)
FROM Bookings
ORDER BY ArrivalDate



I thought this looks familiar. But in the other thread his boss has taken it to the next level.



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 #1422371
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