Re: NULL = NULL not working

From: we7313 (we7313_at_discussions.microsoft.com)
Date: 12/05/04

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    Date: Sun, 5 Dec 2004 07:07:01 -0800

    "Hugo Kornelis" wrote:

    > On Sat, 4 Dec 2004 15:53:05 -0800, we7313 wrote:
    >
    > >I have a proc that can specify a price range if its passed in.
    > >my and where clause looks like this:
    > >
    > >where ((PriceViewHotelPrice.price + PriceViewAirPrice.price)between 500 and
    > >600) or(NULL = NULL))
    > >
    > >I have removed the parameters & replaced them with the values passed in
    > >running it through Sql Analyzer & have confirmed the problem.
    > >If I replace NULL = NULL with 'a' = 'a' it works fine. Does anyone see the
    > >problem with this?
    >
    > Hi we7313,
    >
    > This is working as designed. Using ANSI-standard behaviour for NULLs, NULL
    > is never equal to anything. Think of NULL as an unknown value. If you
    > asked you if an unknown value is equal to an unknown value, would you say
    > "yes", "no" or "no idea"?
    > Welcome in the wonderfull world of three-valued logic!
    >
    > This being said, I'm not sure what you're trying to accomplish and why you
    > are trying to do it this way. Could you explain your actual problem
    > instead of presenting only a partial solution? There might be other, maybe
    > even better ways to solve your problem.
    >
    > If you describe the problem, it would be helpfull to include table
    > structure (as CREATE TABLE statements, including all constraints), sample
    > data (as INSERT statements) and expected output - that often helps getting
    > across what you try to do AND it's a useful testing aid.
    >
    > Best, Hugo
    > --
    >
    > (Remove _NO_ and _SPAM_ to get my e-mail address)
    >

    Well now that you say that & sql books online confirms it, I see why it
    isn't working. The reason I do a statement like above is to apply optional
    criteria based on the parameter values passed in. Thanks for the help.

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