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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6008) Allow ORDER BY and FETCH/OFFSET in set operands
Date Fri, 07 Dec 2012 13:21:20 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6008?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13526374#comment-13526374
] 

Dag H. Wanvik commented on DERBY-6008:
--------------------------------------

Thanks, Knut. I agree the intersect looks wrong indeed. As for the anomaly in values 1 order
by 1+2, I guess this is because the logic to analyze the order by in this case resides in
RowResultSetNode, not in UnionNode/SetOperatorNode as in the multi-valued case. I'd guess
an omission since it's a corner case.

                
> Allow ORDER BY and FETCH/OFFSET in set operands
> -----------------------------------------------
>
>                 Key: DERBY-6008
>                 URL: https://issues.apache.org/jira/browse/DERBY-6008
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Dag H. Wanvik
>            Assignee: Dag H. Wanvik
>         Attachments: derby-6008-a.diff, derby-6008-a.stat, derby-6008-b.diff, derby-6008-b.stat,
derby-6008-c.diff, derby-6008-c.stat
>
>
> Currently, Derby doesn't allow ORDER BY nested in a set operand, e.g. in the following
construct:
> (select i from t1 order by j offset 1 row)    union 
> (select i from t2 order by j desc offset 2 rows)
> This is allowed by the standard, as far as I can understand, cf. this quote from section
7.12 in SQL 2011:
> <query expression body> ::=
>     <query term>
> |   <query expression body> UNION [ ALL | DISTINCT ]
>   [ <corresponding spec> ] <query term>
> |   <query expression body> EXCEPT [ ALL | DISTINCT ]
>   [ <corresponding spec> ] <query term>
> <query term> ::=
>    <query primary>
> |  <query term> INTERSECT [ ALL | DISTINCT ]
>    [ <corresponding spec> ] <query primary>
> <query primary> ::=
>    <simple table>
>   |  <left paren> <query expression body>
>      [ <order by clause> ] [ <result offset clause> ] [ <fetch first clause>
] <right paren>
> I.e. the left paren chooses the second alternative in the production for <query primary>.

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