[jira] Commented: (DERBY-495) COALESCE

["Christian d'Heureuse (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/DERBY-495?page=comments#action_12445317 ] 
            
Christian d'Heureuse commented on DERBY-495:
--------------------------------------------

COALESCE is an important function and should be documented.

In ISO/IEC 9075, the syntax for COALESCE is
  COALESCE ( expression [,expression].... )
but Derby currently does not allow COALESCE with a single argument.
As long as this is not fixed, the syntax documentation should be
  COALESCE ( expression, expression [,expression].... )

In ISO 9075-2, COALESCE is defined as:
  COALESCE (V1, V2) is equivalent to the following <case specification>:
    CASE WHEN V1 IS NOT NULL THEN V1 ELSE V2 END
  COALESCE (V1, V2, ..., Vn), for n ≥ 3, is equivalent to the following <case specification>:
    CASE WHEN V1 IS NOT NULL THEN V1 ELSE COALESCE (V2, ..., Vn) END
This could be used for the documentation.

I wouldn't document that "VALUE is another name for the COALESCE function" in Derby, because thats an "inheritance" from DB2 and not part of the SQL standard.

> COALESCE
> --------
>
>                 Key: DERBY-495
>                 URL: http://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
>            Priority: Minor
>
> The COALESCE function has been implemeted since 10.0.2.0 (at least) but isn't documented.

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