Groups > comp.databases.ms-sqlserver > #1847

Re: CASE issue

From	Lennart Jonsson <erik.lennart.jonsson@gmail.com>
Newsgroups	comp.databases.ms-sqlserver
Subject	Re: CASE issue
Date	2014-11-24 17:18 +0100
Organization	A noiseless patient Spider
Message-ID	<m4vlom$q0c$1@dont-email.me> (permalink)
References	<547306f8$0$41749$c3e8da3$5d8fb80f@news.astraweb.com> <XnsA3EF7E8B63B6CYazorman@127.0.0.1>

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On 11/24/2014 12:26 PM, Erland Sommarskog wrote:
> twenty-six@b-mint.net (twenty-six@b-mint.net) writes:
>> When I run this query I get lots of 'Unknown'  values, but I'm not sure
>> why.
>
> This happens because
>
>      CASE expr WHEN val1 THEN ....
>                WHEN val2 THEN ....
>
> is a shortcut for
>
>     CASE WHEN expr = val1 THEN
>          WHEN expr = val2 THEN
>
> and thus the expression gets evaluated multiple times and then it goes
> downhill from there.
>

I think (don't have time to look it up now) the SQL-standard says that 
the result of the CASE statement is the first condition that evaluates 
to true. From your answer I get the impression that this is not true for 
SQL-server, correct?

Surely only one value is returned, but is it indeterministic which one?

/Lennart

[...]

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CASE issue "twenty-six@b-mint.net" <twenty-six@b-mint.net> - 2014-11-24 10:22 +0000
  Re: CASE issue Erland Sommarskog <esquel@sommarskog.se> - 2014-11-24 11:26 +0000
    Re: CASE issue bradbury9 <ray.bradbury9@gmail.com> - 2014-11-24 04:16 -0800
      Re: CASE issue Erland Sommarskog <esquel@sommarskog.se> - 2014-11-24 14:28 +0000
        Re: CASE issue Erland Sommarskog <esquel@sommarskog.se> - 2014-11-28 22:47 +0100
          Re: CASE issue Jim <jgeissman@socal.rr.com> - 2014-11-28 17:19 -0800
    Re: CASE issue "twenty-six@b-mint.net" <twenty-six@b-mint.net> - 2014-11-24 13:32 +0000
      Re: CASE issue Erland Sommarskog <esquel@sommarskog.se> - 2014-11-24 14:25 +0000
        Re: CASE issue "twenty-six@b-mint.net" <twenty-six@b-mint.net> - 2014-11-24 16:06 +0000
    Re: CASE issue Lennart Jonsson <erik.lennart.jonsson@gmail.com> - 2014-11-24 17:18 +0100
      Re: CASE issue Erland Sommarskog <esquel@sommarskog.se> - 2014-11-24 23:37 +0100
        Re: CASE issue Lennart Jonsson <erik.lennart.jonsson@gmail.com> - 2014-11-25 06:25 +0100
          Re: CASE issue Jim <jgeissman@socal.rr.com> - 2014-11-28 16:07 -0800
            Re: CASE issue Erland Sommarskog <esquel@sommarskog.se> - 2014-11-29 10:43 +0100

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