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https://issues.apache.org/jira/browse/JENA-1856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17054918#comment-17054918
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Andy Seaborne commented on JENA-1856:
-------------------------------------
Hi [~benjamingeer]
If GROUP_CONCAT has an unbound value in the list of values to concat, the
overall result is "error".
This is because {{CONCAT(unbound "foo")}} is error.
Try:
{noformat}
SELECT
(GROUP_CONCAT(if(bound(?decimal),str(?decimal),"UNDEF1"); SEPARATOR=';') AS
?decimal__Concat)
(GROUP_CONCAT(if(bound(?boolean),str(?boolean),"UNDEF2"); SEPARATOR=';') AS
?boolean__Concat)
{noformat}
If you don't want unbounds, even using "" (which will add the ";") then remove
them in the WHERE clause.
> Unexpected results with GROUP_BY and GROUP_CONCAT
> -------------------------------------------------
>
> Key: JENA-1856
> URL: https://issues.apache.org/jira/browse/JENA-1856
> Project: Apache Jena
> Issue Type: Question
> Components: Jena
> Affects Versions: Jena 3.14.0
> Reporter: Benjamin Geer
> Priority: Major
> Attachments: query-with-group-concat.txt,
> query-without-group-concat.txt, test-data.txt
>
>
> Attached is:
> * some example data
> * a query that works as I expected, without {{GROUP BY}}
> * the same query with {{GROUP BY}} and {{GROUP_CONCAT}} added, which doesn't
> work as I expected
> Am I doing something wrong, or is this a bug?
> Using the query without {{GROUP BY}}, I get these results as expected:
>
> ||thing||decimal||boolean||
> |<http://example.org/data/a>| |<http://example.org/data/a/values/2>|
> |<http://example.org/data/b>| |<http://example.org/data/b/values/2>|
> |<http://example.org/data/b>|<http://example.org/data/b/values/1>| |
>
> Using the query with {{GROUP BY}} and {{GROUP_CONCAT}}, I expected to get:
> ||thing||decimal__Concat||boolean__Concat||
> |<http://example.org/data/a>| |<http://example.org/data/a/values/2>|
> |<http://example.org/data/b>|<http://example.org/data/b/values/1>|<http://example.org/data/b/values/2>|
>
> But instead I get:
> ||thing||decimal__Concat||boolean__Concat||
> |<http://example.org/data/a>| |<http://example.org/data/a/values/2>|
> |<http://example.org/data/b>| | |
>
> Should I be doing something different to get the results I expected?
>
>
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