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https://issues.apache.org/jira/browse/DERBY-2351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574648#action_12574648
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A B commented on DERBY-2351:
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Hi Bryan, thanks for the patch. Two minor comments:
1. Slight whitespace inconsistency (w.r.t. existing code) in ResultColumn.java
2. The following query (pulled from your modified orderby.out) currently fails
with error 42X79:
+ij> select distinct name as age from person order by person.age;
+ERROR 42X79: Column name 'AGE' appears more than once in the result of
the query expression.
It's good that the query fails, but I wonder if error 42X79 is the best error
here? From the user's perspective there is only a single column in the query's
result list, so the error seems slightly misleading. Instead, I think error
42879 (added as part of this issue) is more appropriate, since the query
attempts to order by a column that is not in the DISTINCT list. Any idea how
hard it would be to catch that scenario and throw 42879 instead of 42X89?
Would this just be a matter of checking to see if the column was "pulled" into
the select list and, if so, throwing 42879 instead of 42X79? Or is it more
complicated than that? I don't think this is a big deal at all--as long as
there is an error I think it's fine--but I thought I'd ask the question to see
if you have already considered it.
> 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, 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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