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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4371) Non-selected columns for SELECT DISTINCT allowed in ORDER BY clause if ordered by expression
Date Wed, 28 Apr 2010 03:34:33 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12861661#action_12861661

Bryan Pendleton commented on DERBY-4371:

It sounds like your proposed patch would cause
a query which previously passed to get an error instead.

This is the sort of thing that we always think very carefully
about, because people may be currently using queries
like this, and depending on them, and so we are hesitant
to disrupt functionality that is currently operational for fear
of breaking existing applications.

In this particular case, we can see by using the Subversion "annotate" feature
 that the particular query was changed by DERBY-2351 in revision 637529:

I think that the next step is probably to have a close review of the
DERBY-2351 notes and try to understand why the DERBY-2351 changes
are in conflict with the changes in your proposed patch.

It's quite possible that your patch is implementing the desired behavior,
but it would better still if we can understand why DERBY-2351 felt that
the other behavior was desirable.

> Non-selected columns for SELECT DISTINCT allowed in ORDER BY clause if ordered by expression
> --------------------------------------------------------------------------------------------
>                 Key: DERBY-4371
>                 URL: https://issues.apache.org/jira/browse/DERBY-4371
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions:
>            Reporter: Bernt M. Johnsen
>            Assignee: C.S. Nirmal J. Fernando
>            Priority: Critical
>         Attachments: DERBY-4371-2.diff, DERBY-4371.diff
> How to repeat:
> ij> create table t (i integer, j integer);;
> 0 rows inserted/updated/deleted
> ij> insert into t values (1,2),(1,3);
> 2 rows inserted/updated/deleted
> ij> select distinct i from t order by j;
> ERROR 42879: The ORDER BY clause may not contain column 'J', since the query specifies
DISTINCT and that column does not appear in the query result.
> ij> select distinct i from t order by j*2;
> I          
> -----------
> 1          
> 1          
> 2 rows selected

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