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From "Kim Haase (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-495) COALESCE
Date Tue, 11 Aug 2009 15:14:14 GMT

    [ https://issues.apache.org/jira/browse/DERBY-495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12741904#action_12741904
] 

Kim Haase commented on DERBY-495:
---------------------------------

Dag Wanvik has answered the questions that seemed to be holding up the resolution of this
issue.

> > Neither COALESCE nor VALUE is documented currently (except for a
> > mention in an error message).
> >
> > Looking at DERBY-495, it appears that the doc effort stalled for lack
> > of answers to a couple questions --
> >
> > I gather VALUE as a synonym of COALESCE is not in the SQL standard,
> > but COALESCE itself is? Should we mention VALUE, then?

Yes, since it is implemented we should document it as a synonym, but
probably recommend the standard form COALESCE.

> >
> > What does the SQL standard say about the one-argument form? Is it
> > permitted?

The standard does not allow the one-argument form:

SQL 2003, vol 2 section 6.1 <case expression>:
:
<case abbreviation> ::=
  NULLIF <left paren> <value expression> <comma> <value expression>
<right paren>
| COALESCE <left paren> <value expression> { <comma> <value expression>
}... <right paren>

This means that 2 or more args are allowed.
Derby does not permit one argument; it throws 42605.  Also, not all arguments
can be dynamic (?), if so Derby throws 42610.


> COALESCE
> --------
>
>                 Key: DERBY-495
>                 URL: https://issues.apache.org/jira/browse/DERBY-495
>             Project: Derby
>          Issue Type: Bug
>          Components: Documentation
>    Affects Versions: 10.0.2.0
>         Environment: n/a
>            Reporter: Paul Jenkins
>            Assignee: Kim Haase
>            Priority: Minor
>
> The COALESCE function has been implemeted since 10.0.2.0 (at least) but isn't documented.

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