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From "Knut Anders Hatlen (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 Thu, 19 Aug 2010 16:00:21 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12900327#action_12900327
] 

Knut Anders Hatlen commented on DERBY-4371:
-------------------------------------------

> Should we allow following type of queries:
> "select distinct i from t order by i/j;"

No, this query should not be allowed. Consider the table

 i  |  j  | i/j
---------------
100 |  10 | 10
100 | 100 |  1
200 |  40 |  5
  3 |   1 |  3

Here, the ORDER BY clause is ambiguous, because it's not clear whether
100 should be the first value or the last value in the result.

> 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: 10.5.1.1
>            Reporter: Bernt M. Johnsen
>            Assignee: C.S. Nirmal J. Fernando
>            Priority: Critical
>         Attachments: DERBY-4371-2.diff, DERBY-4371-3.diff, DERBY-4371-4.diff, derby-4371-5.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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