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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4406) Wrong order when using ORDER BY on non-deterministic function
Date Mon, 19 Apr 2010 09:38:50 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12858432#action_12858432
] 

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

I'm leaning toward the same conclusion as Bryan, that we should close the issue as "won't
fix". Users can always specify explicitly which behaviour they want by using correlation names,
which will also make the SQL statements clearer. So it's probably not worth the effort or
the risk of breaking old applications that depend on the current behaviour.

> Are there functions other than RANDOM() which exhibit this behavior?

No built-in functions that I'm aware of, but you can create non-deterministic user-defined
functions which behave similarly. (After DERBY-3570, it's even possible to tell CREATE FUNCTION
whether or not the function is deterministic.)

> 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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