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DateAdd Function


DateAdd Function

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HanShi
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Mike John (3/4/2009)
Alternative answer is :

2009-09-02 17:30:00.000 -- which is exactly what you will see if you are configured for a UK date format. ie the dateadds behave as described by the input date is in an ambiguous format... was it the 2nd Sept or 9th Feb?

Mike John

That's only an issue if the year is mentioned at the end (02-09-2009). When the year is mentioned first it's always yyyy-mm-dd, many times also noted without the dashes (20090902).

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Ninja's_RGR'us
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webrunner (3/4/2009)
***********SPOILER ALERT***********

john.arnott (3/3/2009)
For one additional degree of difficulty: What's the result from this query?

select DATEADD(HOUR,5,DATEADD(MINUTE,-59,'2009-02-09 12:34:56.789'))


a) 2009-02-09 07:34:57.789
b) 2009-02-09 16:35:56.789
c) 2009-02-09 16:33:56.790
d) 2009-02-09 16:35:56.790


I'm going to go with:
b) 2009-02-09 16:35:56.789

UPDATE: I ran the result and got c) 2009-02-09 16:33:56.790. (My original second choice.) Why do the milliseconds get rounded up?

Thanks,
webrunner


It's the limit of the precision in ms. If the last digit is not a possible value, it gets rounded up or down depending on the closest number.
Dietmar Weickert
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HanShi (3/4/2009)
Mike John (3/4/2009)
Alternative answer is :

2009-09-02 17:30:00.000 -- which is exactly what you will see if you are configured for a UK date format. ie the dateadds behave as described by the input date is in an ambiguous format... was it the 2nd Sept or 9th Feb?

Mike John

That's only an issue if the year is mentioned at the end (02-09-2009). When the year is mentioned first it's always yyyy-mm-dd, many times also noted without the dashes (20090902).


Well, that's exactly what I would have expected. Nevertheless, when I copy & pasted the given statement

SELECT DATEADD(MINUTE,30,DATEADD(hour,7,'2009-02-09 10:00:00:000'))



into SS Studio Express and pressed F5, my result was

2009-09-02 17:30:00.000



Rather confuses me... Unsure

Best regards,
Dietmar Weickert.
David Burrows
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YYYY-xx-xx will be interpreted as

YYYY-MM-DD or YYYY-DD-MM depending on the connection's language setting


Far away is close at hand in the images of elsewhere.

Anon.


Shaun McGuile
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David: we are going off topic.

I think we all agree that again we have a QoD which is not locale neutral.

This can cause issues with selecting a correct answer.

We need better questions. Smile

Hiding under a desk from SSIS Implemenation Work Crazy
David Burrows
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David: we are going off topic.


Quite Ermm

I think we all agree that again we have a QoD which is not locale neutral.


Yep Wink

My post was not meant to cause offence or consternation in any way Blush


Far away is close at hand in the images of elsewhere.

Anon.


webrunner
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Ninja's_RGR'us (3/4/2009)


...
I'm going to go with:
b) 2009-02-09 16:35:56.789

UPDATE: I ran the result and got c) 2009-02-09 16:33:56.790. (My original second choice.) Why do the milliseconds get rounded up?

Thanks,
webrunner


It's the limit of the precision in ms. If the last digit is not a possible value, it gets rounded up or down depending on the closest number.


Thanks, but could you explain in more detail what happened? I still don't quite understand how the rounding works in this case.

For example, I ran this:
select DATEADD(MINUTE,-59,'2009-02-09 12:34:56.785')

and got this:
2009-02-09 11:35:56.787

I know SQL is doing something to get that result, but if anything I thought it would end in .786 in this case, yet it ends in .787.

Thanks again!
webrunner

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Chad Crawford
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webrunner,
.786 isn't a valid millisecond for the datetime datatype...

All datetimes end in either .xx0, .xx3 or .xx7
.xx9, .xx0 and .xx1 are rounded up/down to .xx0
.xx2, .xx3, .xx4 are rounded up/down to .xx3
.xx5, .xx6, .xx8 are rounded up/down to .xx7

Check out the BOL "Date and Time" for an example table.

Thanks,
Chad
webrunner
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Chad Crawford (3/4/2009)
webrunner,
.786 isn't a valid millisecond for the datetime datatype...

All datetimes end in either .xx0, .xx3 or .xx7
.xx9, .xx0 and .xx1 are rounded up/down to .xx0
.xx2, .xx3, .xx4 are rounded up/down to .xx3
.xx5, .xx6, .xx8 are rounded up/down to .xx7

Check out the BOL "Date and Time" for an example table.

Thanks,
Chad


Wow, that is odd (well, except for .xx0 Smile), but thank you so much for telling me. I never would have figured it out, and there it is spelled out in BOL.

Thanks again,
webrunner

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Ref.: http://tkyte.blogspot.com/2009/02/sql-joke.html
notquitexena
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I thought it was a dead giveaway that only one answer had the correct date prefix (2009-02-09). The wrong answers had 2009-02-10 and 2009-02-08. Except for clicking on the wrong button on mistake, I can't understand why anyone would miss this question.
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