[
https://issues.apache.org/jira/browse/DERBY-6819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14590898#comment-14590898
]
Craig Chaney commented on DERBY-6819:
-------------------------------------
I was able to work around this by changing the order of the joins, like:
select e.PART_NAME as ENGINE, b.PART_NAME as BODY, count(distinct m.ID) as
NUM_MODELS from CARS.MODELS m
left outer join CARS.TOP_SPEED s on m.ID=s.ID
left outer join CARS.PART_NAMES e on m.ENGINE_ID=e.ID
left outer join CARS.PART_NAMES b on m.BODY_ID=b.ID
where s.SPEED>50
group by e.PART_NAME, b.PART_NAME
> incorrect results from a multi-column group by query
> ----------------------------------------------------
>
> Key: DERBY-6819
> URL: https://issues.apache.org/jira/browse/DERBY-6819
> Project: Derby
> Issue Type: Bug
> Components: JDBC, SQL
> Affects Versions: 10.10.2.0, 10.11.1.1
> Environment: Ubuntu Linux, Java 6, JDBC
> Reporter: Craig Chaney
> Attachments: sample_db.sql
>
>
> I'm getting some strange results from a specific pattern of queries related
> to finding a count of columns grouped in two dimensions.
> The following query works as I would expect:
> select e.PART_NAME as ENGINE, b.PART_NAME as BODY, count(distinct m.ID) as
> NUM_MODELS from CARS.MODELS m
> left outer join CARS.PART_NAMES e on m.ENGINE_ID=e.ID
> left outer join CARS.PART_NAMES b on m.BODY_ID=b.ID
> group by e.PART_NAME, b.PART_NAME
> This returns something like:
> ENGINE BODY NUM_MODELS
> electric compact 1
> gas compact 2
> gas sedan 1
> gas truck 2
> hybrid compact 1
> hybrid sedan 2
> So this fictitious car company sells 2 different hybrid sedans, one gas sedan
> etc.
> If I add a filter to the query that should not actually change the output, I
> see output that doesn't make sense.
> This query filters out any car whose top speed is less than 50 (and all cars
> have a top speed higher than this):
> select e.PART_NAME as ENGINE, b.PART_NAME as BODY, count(distinct m.ID) as
> NUM_MODELS from CARS.MODELS m
> left outer join CARS.PART_NAMES e on m.ENGINE_ID=e.ID
> left outer join CARS.PART_NAMES b on m.BODY_ID=b.ID
> left outer join CARS.TOP_SPEED s on m.ID=s.ID
> where s.SPEED>50
> group by e.PART_NAME, b.PART_NAME
> The results show the wrong values in column 2:
> ENGINE BODY NUM_MODELS
> electric electric 1
> gas gas 2
> gas gas 1
> gas gas 2
> hybrid hybrid 1
> hybrid hybrid 2
> I've tried the same query on DB2 with the same data and I get the results
> that I expect -- that is, both queries return the same result that I showed
> on the first query here.
> I'll attach a script that creates a database with the sample data used above.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
