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https://issues.apache.org/jira/browse/DERBY-2351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12575469#action_12575469
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A B commented on DERBY-2351:
----------------------------
Army> it seems reasonable to throw an error instead of returning wrong
results--as long
Army> as we indicate to users that such a change happens.
Perhaps this is obvious, but it occurs to me that the difference between the
query being discussed and the query that was originally disallowed by changes
for this Jira is that the latter was disallowed because the semantics are not
defined, while the former has a well-defined behavior that Derby fails to
accomplish. I don't think this changes the fact that it's (probably) better to
throw an error than to allow wrong results, but I *do* think that if a commit
is made which causes the second query (from Bryan's Mar 03 comments) to start
throwing an error (instead of returning results in the wrong order), it would
be good to file another Jira defect to indicate that such an error is due to a
known (current) Derby limitation.
> 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: 10.3.2.2, 10.4.0.0
>
> Attachments: d2351_aliasing.diff, d2351_aliasing.diff,
> 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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