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https://issues.apache.org/jira/browse/DERBY-4371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12862039#action_12862039
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C.S. Nirmal J. Fernando commented on DERBY-4371:
------------------------------------------------
Hi Bryan,
As I understood after going through DERBY-2351, we must allow queries like:
select distinct i from t order by i*2
should be allow as this functionality may have been using by Derby
users, in there applications. Derby allows this is because i is there in the
distinct even though i*2 is not there.
So, if we follow this rule it implies that:
select distinct * from t order by i*2
is also allow.
To check whether a column reference in a distinct is contained in this order by
column I have to perform a check for each operand in both ways (j*2 and 2*j).
I have attached a patch proposal. Your reviews are highly appreciated.
Note: This patch is not tend to handle queries like below:
select distinct i from t order by random()
select distinct i from t order by j*2*3;
Thanks.
> 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.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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