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Date conversions

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DonAtWork
Master Smack Fu Yak Hacker

2167 Posts

Posted - 2012-09-12 : 10:34:19

I was messing with some dates, and found a quick little bit that changed a date to the 1st day of the month:

declare @d date = '11/23/2012'
SELECT DATEADD(mm, 0 + DATEDIFF(mm, 0, @d), 0)

Naturally, someone now needed a date converted to the 1st day of a quarter. This little algorithm assumes that quarters start Jan 1st.

SELECT DATEADD(mm, - CASE 
		     WHEN (MONTH(DATEADD(mm, 0 + DATEDIFF(mm, 0, @d), 0) )% 3)  > 0 
		     THEN ((MONTH(DATEADD(mm, 0 + DATEDIFF(mm, 0, @d), 0) )% 3) -1) 
		     ELSE 2 END 
                     ,DATEADD(mm, 0 + DATEDIFF(mm, 0, @d), 0)
	       )

Any suggestions or comments would be appreciated.

How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx

robvolk
Most Valuable Yak

15732 Posts

Posted - 2012-09-12 : 10:51:10

Why not just use SELECT DATEADD(q, 0 + DATEDIFF(q, 0, @d), 0) ?

DonAtWork
Master Smack Fu Yak Hacker

2167 Posts

Posted - 2012-09-12 : 11:06:10

umm.. because that is way too readable?

How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx

jeffw8713
Aged Yak Warrior

819 Posts

Posted - 2012-09-12 : 13:44:26

You can simplify both of your equations by removing the '0 +' before the DATEDIFF.

SELECT DATEADD(month, DATEDIFF(month, 0, GETDATE()), 0);

For a little variation:

DECLARE @numMonths int;
SET @numMonths = -3;

SELECT DATEADD(month, DATEDIFF(month, 0, GETDATE()) - @numMonths), 0);
SELECT DATEADD(month, DATEDIFF(month, -1, GETDATE()) - @numMonths), -1);

Swap out month for any other date interval and see what happens.

Jeff

madhivanan
Premature Yak Congratulator

22864 Posts

Posted - 2012-09-13 : 02:04:56

Go to the last section of this post and find more such methods
http://beyondrelational.com/modules/2/blogs/70/posts/10899/understanding-datetime-column-part-iii.aspx

Madhivanan

Failing to plan is Planning to fail

madhivanan
Premature Yak Congratulator

22864 Posts

Posted - 2012-09-13 : 02:10:47

quote:
Originally posted by DonAtWork

umm.. because that is way too readable?

How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx

Thats a good excuse

Madhivanan

Failing to plan is Planning to fail

DonAtWork
Master Smack Fu Yak Hacker

2167 Posts

Posted - 2012-09-14 : 06:51:54

quote:
Originally posted by madhivanan

Go to the last section of this post and find more such methods
http://beyondrelational.com/modules/2/blogs/70/posts/10899/understanding-datetime-column-part-iii.aspx

Madhivanan

Failing to plan is Planning to fail

LOVE that post. Very useful!

How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx

madhivanan
Premature Yak Congratulator

22864 Posts

Posted - 2012-09-14 : 07:21:53

quote:
Originally posted by DonAtWork

quote:
Originally posted by madhivanan

Go to the last section of this post and find more such methods
http://beyondrelational.com/modules/2/blogs/70/posts/10899/understanding-datetime-column-part-iii.aspx

Madhivanan

Failing to plan is Planning to fail

LOVE that post. Very useful!

How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx

Thanks

Madhivanan

Failing to plan is Planning to fail

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