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https://issues.apache.org/jira/browse/DERBY-2351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12570033#action_12570033
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A B commented on DERBY-2351:
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> It was not the intent of this change to reject the alias form of the query
> [...]
Okay, thank you for the reply, Bryan. And thanks for the investigation that
you've done to reply so thoroughly.
> However, it is not clear to me whether that query ought to be allowed or not
> [...]
>From the various responses to the user thread referenced in my previous
>comment, it sounds like different databases treat this kind of thing
>differently. So I don't know what the "best" behavior would be here, either...
For the record, I was merely asking the question because a query which worked
in one release stopped working in the next, with no clear explanation as to
why. The response on the user list was generally "well that doesn't work in
some other databases, so don't do it; use the alias instead"--which is fine as
a workaround, but it left me wondering why the behavior changed between
releases to begin with. Your reply above filled in the missing information for
me--so thanks!
> I think we need to spend some time understanding how the SQL Standard intends
> that the ORDER BY, GROUP BY, and HAVING clauses should behave [...]
If the standard lays it all out, then I agree, that certainly seems like a good
way to go...
> ORDER BY with expression with distinct in the select list returns incorrect
> result
> ----------------------------------------------------------------------------------
>
> Key: DERBY-2351
> URL: https://issues.apache.org/jira/browse/DERBY-2351
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.2.1.6, 10.2.2.0, 10.3.1.4
> Environment: Any
> Reporter: Yip Ng
> Assignee: Bryan Pendleton
> Fix For: 10.3.2.1, 10.4.0.0
>
> Attachments: derby_2351.diff, derby_2351_v2.diff, reproTests.diff
>
>
> When distinct is in the select list and the query has order by with
> expression, the resultset produced contains an additional column.
> ij> create table t1 (c1 int, c2 varchar(10))
> 0 rows inserted/updated/deleted
> ij> insert into t1 values (1,'a'),(2,'b'),(3,'c');
> 3 rows inserted/updated/deleted
> select distinct c1, c2 from t1 order by c1;
> C1 |C2
> ----------------------
> 1 |a
> 2 |b
> 3 |c
> 3 rows selected
> ij> select distinct c1, c2 from t1 order by c1+1;
> C1 |C2 |3 <=====returns 3
> columns, incorrect result returned
> ----------------------------------
> 1 |a |2
> 2 |b |3
> 3 |c |4
> 3 rows selected
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