Know Your SQL Objects

  • Ya 1 point definitely underkill for this one.

    Maybe Steve's MCM training has skewed his judgement a little bit... you're getting too good Stevie! :hehe:

  • I got caught by the wording of Extents can be owned by only one object as well.

    Maybe a language issue, but I interpreted it as the complementary answer to Extents can be owned by multiple objects.

    With regards to Text data is stored on data pages, this is debatable. It depends on the options you have set up for your table (table option "text in row", http://msdn.microsoft.com/en-us/library/ms173530.aspx) and on the size of the data you are trying to store.

    But I would not have included the Text data part at all in the QOTD, since this is deprecated and ancient 😛

    Best Regards,

    Chris Büttner

  • I'm also caugth by the Extent owner case. Maybe next time you should write "might" instead of "can".

  • This question reminds me of my grad school and teaching days. Some people people feel that to make a challenging question, there has to be a semantic trick to the way the question is asked. This frequently occurs when the person asking the question is so sure of the answer that they fail to put themselves in the place of the person asked to answer the question. They don't see that the question is phrases in a possibly confusing manner. With a question like that, you're not testing subject knowledge, you're testing test taking skill. And, I might mention it places an extra burden on the nonnative speaker of the language - someone who is not as well equipped to ferret out the subtleties in the question.

    Or, these questions can be developed by someone with a (hidden or not) sadistic streak that takes joy in the semantic trick itself.

    To bad, as this has marred an otherwise good question that forced me to learn something I didn't know. Always good.

    Disclaimer: The above is motivated by having only got 3 of 4 correct.

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  • John Mitchell-245523 (5/13/2011)


    ... But, as has been pointed out, it's the discussion and what you learn that's important, not the points.

    John

    Says you! You can buy tons of things with your points. From airline upgrades and stores to pork chop flingers and time warps. If you don't want your points, give them to me please, I almost have enough for the "I'm a DBA" button.

    source

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  • tabraham 36699 (5/13/2011)


    This question reminds me of my grad school and teaching days. Some people people feel that to make a challenging question, there has to be a semantic trick to the way the question is asked. This frequently occurs when the person asking the question is so sure of the answer that they fail to put themselves in the place of the person asked to answer the question.

    Disclaimer: The above is motivated by having only got 3 of 4 correct.

    I get the disclaimer, but I did want to clarify something.

    I actually did agonize over my word choice there. I went over it three or four times (because I'm a writer and I know semantics do matter) before making my final, and deliberate, choice of wording on the Extents answers. I even changed it from a more confusing answer that would have come across as one or the other (mixed or uniform).

    The thing is, as much as I try, I can't account for every single possible interpretation of the word "can." I did the best I could. But the biggest hurdle to overcome is physiological (how the brain actually functions), not mental (no mind games here). I.E., most people don't actually read a whole sentence. The brain is processing so fast, it picks out the 4-5 most important words and "assumes" the rest, filling the meaning in based on experience and memory.

    Don't believe me? Then I have an interesting exercise for you to try.

    Start paying a bit more attention to your reading habits. Read posts, blogs and a book page as normal. Write down what you think you read, then go back and actually read every single word to see how different it is from what you thought you read. You'll be about 75%-90% correct with your interpretation, but find a few minor details that you missed or misconstrued. I've tested this before and know several other people who tried it too. It's amazing how my outlook changed once I realized how many assumptions my brain actually makes.

    EDIT: Another reason why Brain Dumps don't work and why people fail on cert exams they should otherwise pass.

    Brandie Tarvin, MCITP Database AdministratorLiveJournal Blog: http://brandietarvin.livejournal.com/[/url]On LinkedIn!, Google+, and Twitter.Freelance Writer: ShadowrunLatchkeys: Nevermore, Latchkeys: The Bootleg War, and Latchkeys: Roscoes in the Night are now available on Nook and Kindle.

  • Again, this is a good question Brandie, and I know that it can be hard to write an accurate sentence when it is also supposed to be as short as possible.

    Perhaps a better wording would have been Data pages can be owned by a single object, instead of writing Data pages can be owned by only one object.

  • I have to disagree that Rows can span multiple pages (excluding LOB data) is incorrect.

    Read my previous posts where I give my opinion why it is correct.

  • I can't say I'm surprised I got this one wrong. I kept going back and forth between LOB data including the row overflow pages (which it technically doesn't) and the option about uniform extents being poorly phrased (I wasn't sure if what was meant was "Extents can only be owned by one object" or if it meant what it said). Based on some stuff in the past and the fact that one is is a wording thing I assumed that the wording on uniform extents wasn't as intended and got it wrong. It's good to know that Brandi intentionally chose that wording. Thanks for the question, it certainly made me think about what each means and how they're used.

  • All... Straight from the BOL on my system:

    Page type -- Contents

    Data --

    Data rows with all data, except text, ntext, image, nvarchar(max), varchar(max), varbinary(max), and xml data, when text in row is set to ON.

    Index --

    Index entries.

    Text/Image --

    Large object data types: text, ntext, image, nvarchar(max), varchar(max), varbinary(max), and xml data

    Variable length columns when the data row exceeds 8 KB:

    varchar, nvarchar, varbinary, and sql_variant

    --------------------------------------------------------------

    So I have to agree with those that say "Text feilds are not stored in data pages by default."

    They certainly are also not stored in data pages in my database by rhyme and reason.;-) 😎

  • John Mitchell-245523 (5/13/2011)


    Koen Verbeeck (5/13/2011)


    Nils Gustav Stråbø (5/13/2011)


    "-Extents can be owned by only one object"

    False, since they can be a mixed extent (or even an extent that has not been allocated). Perhaps it's your use of the word "only" that confuses me, but what I read is "an extent must be owned by one, and only one, object."

    The question uses the word can, not must. If an extent can be owned by multiple objects, it can certainly be owned by one object.

    Anyway, nice question, but only one point?

    I'm with Nils on this. The sentence can be interpreted as "it is only possible for an extent to be owned by one object" or as "it is possible for an extent to be owned by only one object". I went for the former and so got it wrong. But, as has been pointed out, it's the discussion and what you learn that's important, not the points.

    John

    The BOL states :

    Uniform extents are owned by a single object; all eight pages in the extent can only be used by the owning object.

    Mixed extents are shared by up to eight objects. Each of the eight pages in the extent can be owned by a different object.

    So yes Extents can be owned by one object or multiple objects. Just depends which type.

  • Nils Gustav Stråbø (5/13/2011)


    Again, this is a good question Brandie, and I know that it can be hard to write an accurate sentence when it is also supposed to be as short as possible.

    Perhaps a better wording would have been Data pages can be owned by a single object, instead of writing Data pages can be owned by only one object.

    I did of course mean extents instead of pages.

  • Oh I believe you. I know that we don't read/see/hear what we think we do, and that the brain usually fills in the gaps in often unpredictable ways. You points are well taken. However, I'd like to give you two items that might demonstrate that that is not all that's going on here:

    1. I missed 2 questions on the Graduate Record Exam. (I'm embarrassed to say they were on the English section.) Just one example that might demonstrate that I'm an above average test taker - implying an above average ability to decipher test questions - ceteris paribus. That doesn't mean I'm immune to the effects you described, it only makes me perhaps less prone to that when taking tests.

    2. As of when I attempted the question, the failure rate was about 90%. That indicates likely one of two things: either the question is highly discriminative at the margin ( only the most knowledgable knew the answer) - or the question was worded in such a way as to lead otherwise knowledgable people into selecting an incorrect answer. To truly determine if the latter is the case, we'd need to have some objective measure of the knowledge level of those who missed the question vs those who got it right. We don't have that. But, if SSC point totals (as meaningful as they are!) can be used as a surrogate, then some pretty high point value people missed the question.

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  • calvo (5/13/2011)


    John Mitchell-245523 (5/13/2011)


    ... But, as has been pointed out, it's the discussion and what you learn that's important, not the points.

    John

    Says you! You can buy tons of things with your points. From airline upgrades and stores to pork chop flingers and time warps. If you don't want your points, give them to me please, I almost have enough for the "I'm a DBA" button.

    source

    Right on Calvo... The entire point system says it is for Bragging rights. Then everyone tries to tell you "Forget about it."

    You keep beliving. Tell Steve the new site need to let people exchange points. Especially if they are starting a new account and want to transfer from an old one.

  • SanDroid (5/13/2011)


    John Mitchell-245523 (5/13/2011)


    Koen Verbeeck (5/13/2011)


    Nils Gustav Stråbø (5/13/2011)


    "-Extents can be owned by only one object"

    False, since they can be a mixed extent (or even an extent that has not been allocated). Perhaps it's your use of the word "only" that confuses me, but what I read is "an extent must be owned by one, and only one, object."

    The question uses the word can, not must. If an extent can be owned by multiple objects, it can certainly be owned by one object.

    Anyway, nice question, but only one point?

    I'm with Nils on this. The sentence can be interpreted as "it is only possible for an extent to be owned by one object" or as "it is possible for an extent to be owned by only one object". I went for the former and so got it wrong. But, as has been pointed out, it's the discussion and what you learn that's important, not the points.

    John

    The BOL states :

    Uniform extents are owned by a single object; all eight pages in the extent can only be used by the owning object.

    Mixed extents are shared by up to eight objects. Each of the eight pages in the extent can be owned by a different object.

    So yes Extents can be owned by one object or multiple objects. Just depends which type.

    I don't dispute that. My point was that the wording of the question was ambiguous. I think Nils has got it spot on with his suggested alternative wording.

    John

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