[ 
http://issues.apache.org/jira/browse/DERBY-280?page=comments#action_12358945 ] 

Kathey Marsden commented on DERBY-280:
--------------------------------------

In an earlier comment you mentioned a valid query which worked before the patch 
which now fails with:

ij> select a+1 as a, a+1 as a from bug280 group by a;
ERROR X0A00: The select list mentions column 'A' twice. This is not allowed in 
queries with GROUP BY or HAVING clauses. Try aliasing one of the conflicting 
columns to a unique name.


There was a discussion of whether this new failure was worth introducing given 
the seriousness of returning wrong results.   A choice of the lesser of evils I 
thought, regress an edge case rather than return wrong results.
But I might have been mistaken.




> Wrong result from select when aliasing to same name as used in group by
> -----------------------------------------------------------------------
>
>          Key: DERBY-280
>          URL: http://issues.apache.org/jira/browse/DERBY-280
>      Project: Derby
>         Type: Bug
>   Components: SQL
>     Reporter: Bernt M. Johnsen
>     Assignee: Rick Hillegas
>     Priority: Minor
>  Attachments: bug280.diff
>
> Wrong result from select when aliasing to same name as used in group by. 
> Example:
> If we have the following table:
>     ij> select * from tt;
>     I          |J
>     -----------------------
>     1          |2
>     2          |3
>     1          |2
>     2          |3
>     2          |3
>                                                                               
>                                                                
>     5 rows selected
> The following select is ok:
>     ij> select i, count(*) as cnt from tt group by i;
>     I          |CNT
>     -----------------------
>     1          |2
>     2          |3
>                                                                               
>                                                                
>     2 rows selected
> But this one returns wrong result in the aliased column:
>     ij> select i, count(*) as i from tt group by i;
>     I          |I
>     -----------------------
>     1          |1
>     2          |2
>                                                                               
>                                                                
>     2 rows selected
>                                                                               
>                                                                

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