db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "C.S. Nirmal J. Fernando (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4406) Wrong order when using ORDER BY on non-deterministic function
Date Thu, 15 Apr 2010 17:51:49 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12857436#action_12857436
] 

C.S. Nirmal J. Fernando commented on DERBY-4406:
------------------------------------------------

Hi,

I found that,
1) "select random() from t order by random()" == "select random() as r from t order by random()"
is considered as a valid query in Postgre SQL.


2) "SELECT i*RANDOM() AS R FROM T ORDER BY i*RANDOM()": In Postgre SQL they're ordering this
by R.


3)"SELECT i, i*RANDOM() AS R FROM T ORDER BY i*RANDOM() ": In Postgre SQL they're ordering
the result set by  i*RANDOM() that means by R.


> 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

-- 
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: https://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

Mime
View raw message