NULL

  • Comments posted to this topic are about the item NULL

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  • An easy one! NULL means a value unknown or not defined yet, it may be equal to or may not be equal to 'Kannur'....Hence NULLS disappear from equality and inequality operations. They are handled separately 🙂

    BTW...thanks for this refreshing question though!

    ~ Lokesh Vij


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  • Thank you for a nice easy question.

    But I'm not sure about explanation (or maybe I'm just reading it wrong):

    The Null value also matches the condition in case of Not Operators (<>,Not in ,Not like..) since it could possibly be a match.

    I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

    --Vadim R.

  • rVadim (8/14/2012)


    I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

    +1

    Yes that's correct!

    ~ Lokesh Vij


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  • Easy question and point today - thanks

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  • Lokesh Vij (8/14/2012)


    rVadim (8/14/2012)


    I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

    +1

    Yes that's correct!

    +1

    And even worse the answer is incorrect with ANSI NULLS off.



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  • Interesting. Thanks for this one.

  • honza.mf (8/15/2012)


    Lokesh Vij (8/14/2012)


    rVadim (8/14/2012)


    I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

    +1

    Yes that's correct!

    +1

    And even worse the answer is incorrect with ANSI NULLS off.

    I did spend some time checking to see if there were any clues as to whether ANSI NULLS was on or off before I answered!

  • Thanks for a nice easy question to celebrate the midweek.

  • Samith, thanks for contributing! Always interesting, and potentially contentious, when NULLs are brought up. But, good to keep thinking of them.

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  • Nice question. This trips up a lot of people new to SQL and seems to lead to a lot of negative feelings towards NULL values.

    (NULLs aren't bad, they're just often misunderstood!!)

  • sestell1 (8/15/2012)


    Nice question. This trips up a lot of people new to SQL and seems to lead to a lot of negative feelings towards NULL values.

    (NULLs aren't bad, they're just often misunderstood!!)

    Totally agree. 🙂

    I actually love NULLS, but then again I'm more familiar with them my devs are.

    The sad thing are the number of tables with NULLable columns, but the apps explode when the data is actually NULL because the guys who made the database 10 years before I started didn't handle NULL correctly, or didn't make the column NOT NULL.

    Ah one day we'll get them all cleaned up... 80 databases.... over 1500 tables used by nearly 50 applications.... probably not soon.



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  • honza.mf (8/15/2012)


    Lokesh Vij (8/14/2012)


    rVadim (8/14/2012)


    I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

    +1

    Yes that's correct!

    +1

    And even worse the answer is incorrect with ANSI NULLS off.

    At leats this thankfully won't be an issue sooner or later. SET ANSI NULLS OFF will throw an error in a coming SQL Release.

    http://msdn.microsoft.com/en-us/library/ms188048.aspx



    --Mark Tassin
    MCITP - SQL Server DBA
    Proud member of the Anti-RBAR alliance.
    For help with Performance click this link[/url]
    For tips on how to post your problems[/url]

  • EZPZ

    Thanks

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