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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4397) Allow ORDER BY in subqueries
Date Wed, 07 Oct 2009 23:53:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12763309#action_12763309
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Dag H. Wanvik commented on DERBY-4397:
--------------------------------------

Thanks for looking at this, Knut, Rick.
@Knut
Re 1), I can't see that ORDER BY should be allowed before a UNION without a (), can you explain
how you reach that conclusion? It seems to me that what comes before the UNION must eventually
come from a <query primary> which is either a table name or a (parenthesized)  subquery..

2) I hope  so, I agree that in an INSERT context, an ORDER BY in the subquery should not be
ignored in the presence of identity columns.
3) Yes that is correct, I was thinking of the case where the ORDER BY is inside a subquery
and the containing query contains a window. Btw, hat case may be covered by an ORDER BY inside
the window specification (equivalently?) when we support that.
4) I am not aware of any such backwards-compatibility issues at this point. I added this as
a reminder to self to check it ;-)

@Rick
Good point about the user guide for INSERT. Will add a note on that.


> Allow ORDER BY in subqueries
> ----------------------------
>
>                 Key: DERBY-4397
>                 URL: https://issues.apache.org/jira/browse/DERBY-4397
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Dag H. Wanvik
>         Attachments: orderBySpec.html
>
>
> SQL 2008 allows ORDER BY to be specified in subqueries. In conjunction with OFFSET/FETCH
and/or ROW_NUMBER
> meaningful subqueries with row ordering may be formulated. Cf. MySQL's LIMIT may be used
in subqueries as well.
> Note that OFFSET/FETCH is currently not allowed in subqueries, either.

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