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From "Kim Haase (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5557) NULLIF topic in reference manual should explain NULLIF
Date Wed, 11 Apr 2012 13:19:17 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13251531#comment-13251531
] 

Kim Haase commented on DERBY-5557:
----------------------------------

Thanks for the advice, Dag and Knut!

I think it would be a good idea to provide a second patch instead of committing this one.
The additional changes would do the following:

1) call NULLIF a function rather than an expression
2) move the CASE expression topic under "SQL expressions" (not sure where; possibly after
"Boolean expressions"?)
3) modify the "SQL expressions" topic (http://db.apache.org/derby/docs/dev/ref/rrefsqlj19433.html)
to add a mention of CASE expressions to the "Conditional expression" row of the first table.
As far as I can tell, conditional expressions include only the CASE expression and the NULLIF
and COALESCE functions, so perhaps all three should be mentioned?

I'll work on this -- if you have more suggestions, or answers to my questions, please go ahead!
                
> NULLIF topic in reference manual should explain NULLIF
> ------------------------------------------------------
>
>                 Key: DERBY-5557
>                 URL: https://issues.apache.org/jira/browse/DERBY-5557
>             Project: Derby
>          Issue Type: Improvement
>          Components: Documentation
>    Affects Versions: 10.8.2.2
>            Reporter: Knut Anders Hatlen
>            Assignee: Kim Haase
>         Attachments: DERBY-5557.diff, rrefcasenullif.html
>
>
> The section describing NULLIF in the reference manual is a bit cryptic. http://db.apache.org/derby/docs/10.8/ref/rrefcasenullif.html
> It says that NULLIF is used for conditional expressions, and that it is similar to CASE,
but it doesn't say in plain words how it works. It would be good if it could mention that
NULLIF returns NULL if the two arguments are equal, and that it returns the first argument
if they are not equal.

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