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Date: Mon, 19 Apr 2010 14:51:50 -0400 (EDT)
From: "Knut Anders Hatlen (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-4406) Wrong order when using ORDER BY on
 non-deterministic function
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    [ https://issues.apache.org/jira/browse/DERBY-4406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12858631#action_12858631 ] 

Knut Anders Hatlen commented on DERBY-4406:
-------------------------------------------

Hi Lily,

If you have two equivalent queries that only differ in whether they use correlation names, the performance should be identical. I think the compiler also adds auto-generated correlation names internally if there is no explicit correlation name given, so there should be no difference at execution time.

> Wrong order when using ORDER BY on non-deterministic function
> -------------------------------------------------------------
>
>                 Key: DERBY-4406
>                 URL: https://issues.apache.org/jira/browse/DERBY-4406
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.5.3.0, 10.6.0.0
>            Reporter: Knut Anders Hatlen
>            Assignee: C.S. Nirmal J. Fernando
>
> If I read the SQL standard correctly, a statement such as "select random() as r from t order by random()" should be treated as "select random() as r from t order by r". Derby does however generate a second, hidden random() column by which the rows are ordered.
> ij> create table t(x int);
> 0 rows inserted/updated/deleted
> ij> insert into t values 1,2,3,4,5;
> 5 rows inserted/updated/deleted
> ij> -- wrong result, not ordered by r
> ij> select random() as r from t order by random();
> R                     
> ----------------------
> 0.1285512465366495    
> 0.5116860880915798    
> 0.21060042130229073   
> 0.2506706923680875    
> 0.6378857329935494    
> 5 rows selected
> ij> -- correct result, ordered by r
> ij> select random() as r from t order by r;
> R                     
> ----------------------
> 0.0749025910679918    
> 0.07694931688380491   
> 0.1724114605785414    
> 0.2268758969382877    
> 0.31900450349277965   
> 5 rows selected

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