TOP and TABLESAMPLE

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TOP and TABLESAMPLE

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Jamie Longstreet-481950

Posted Wednesday, July 30, 2008 9:53 AM

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No apology necessary - I always get them wrong when I am sure I know the answer. I learned something - that's more important than the points (frosting).

Jamie

Post #543658

bitbucket-25253

Posted Wednesday, July 30, 2008 10:12 AM

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DISREGARD THIS RANTING

Correct answer: select top 1000 col1 from bigtable, select top 10 percent col1 from bigtable

I too selected a single answer not multiple answers

KevRiley - please accept my sincere apologies for my stupidity

I have edited my previous 2 posts to reflect the above.

Again - thanks for not kicking my butt too hard, but I deserved it

If everything seems to be going well, you have obviously overlooked something.

Ron

Please help us, help you -before posting a question please read
Before posting a performance problem please read

Post #543670

Christian Buettner-167247

Posted Wednesday, July 30, 2008 10:13 AM

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Finally found the source of confusion:

Which of the following statements is guaranteed to return 1000 rows

instead of

Which of the following statements are guaranteed to return 1000 rows

But the answer possibilities and checkboxes do not leave much room for confusion. (unless one ignores the last 3 answers, which is never a good idea.

Thanks for the very good question, keep it up!

Best Regards,
Chris Büttner

Post #543675

Miles Neale

Posted Wednesday, July 30, 2008 10:16 AM

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Not to cause a problem here but I think that I agree with bitbucket on this one. But there is more to this then a simple question and answer.

The QOTD has been an opportunity for many to learn a little something each day, as well it has been a reminder of what you may already know.

The question was to make a selection for the best answer. It clearly did not say select the best answer or answers, or choose all that apply. As a result we looked at the question as being straight forward. It was not.

The possible intent then of the question might not have been trying to get the right answer but to be deceptive in approach and to reinforce the negative. This also is a powerful tool in learning for you remember those professors and others who pose questions designed to make you fail. They generally are hated at the time and some are never appreciated but they teach us a much more important lesson then a simple sql construct or some class materials. They teach us that we need to be aware at all times no matter who or what we are dealing with, for even the trusted can lead you astray if you are not aware.

The lesson you are providing here is far more important then you know. For those who appear to be telling it like it is, may have an agenda to point you in their direction for their gain instead of pointing at the truth.

Thanks:)

Miles...

Not all gray hairs are Dinosaurs!

Post #543679

kevriley

Posted Wednesday, July 30, 2008 10:22 AM

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bitbucket - no worries - I was only trying to understand how best to help you - so no butt kicking here!

Another lesson learned for me too - must write questions without (too much) ambiguity :D

Kev

Post #543684

Steve Jones - SSC Editor

Posted Wednesday, July 30, 2008 11:30 AM

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OK, this is more my fault than Kevin's.

To start, "is" changed to "are" and "select all that apply" added. I should have done that.

The engine is built to show radio buttons if one answer is required, checkboxes if 2 or more are correct. That's how the MS tests work, but it also means there's a trick. If I forget the "select all the apply", you have to know that at least 2 answers are required. I'm not sure if I'd always like to have checkboxes, though that would remove the confusion from questions.

I also can't an an either/or for partial credit. Enhancement is needed here, but I'm not sure how I can do this without confusing myself more often than not w00t

I thought it was a good question, but I didn't read into it like a few of you. I also see it from a different perspective, so apologies for any confusion. The intent from me, and I'm guessing Kevin, was not to confuse, but show that SAMPLE isn't necessarily accurate.

Follow me on Twitter: @way0utwest

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Post #543743

Steve Jones - SSC Editor

Posted Wednesday, July 30, 2008 12:08 PM

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As an FYI, I'm not upset about the complaints. I completely understand how it looks from your side and I apologize.

The QOD is a hard place to get a good question written. And it's hard to think about all the ways things can be interpreted. You have valid reasons for not liking the question and I hope we've fixed them for people answering now and we'll keep them in mind in the future.

Follow me on Twitter: @way0utwest

Forum Etiquette: How to post data/code on a forum to get the best help

Post #543787

Melville

Posted Friday, August 08, 2008 3:59 AM

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I've been caught out by the multiple answer thang before - but never again!

This argument over lost points is hiding how good a question this is. Who at MS decided that a tablesample of 1000 rows should return *approximately* 1000 rows! I can see that 10 percent might be an approximation - but an exact number of rows! Sheesh.

From BOL:

When a number of rows is specified, rather than a percentage based on the total number of rows in the table, the number is converted into a percentage of the rows, and therefore, pages, that should be returned. The TABLESAMPLE is then performed with that computed percentage.

This is silly.

Post #548976

Jeff Moden

Posted Wednesday, September 10, 2008 7:58 PM

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Wow... although I've not needed to use it, I've heard about TableSample before. Didn't know it would return a random number of rows in the rows mode. What a POS command it is. If you use (10 rows) on a 10,000 row table, you get 0 rows. The guys that put that on together need a porkchop dinner Moden style! :P

--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."

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