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Date: Thu, 28 May 2009 07:54:46 -0700 (PDT)
From: "Bryan Pendleton (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-3002) Add support for GROUP BY ROLLUP
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    [ https://issues.apache.org/jira/browse/DERBY-3002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713996#action_12713996 ] 

Bryan Pendleton commented on DERBY-3002:
----------------------------------------

Hi Knut, thanks again for the notes and observations.

Your point about the handling of empty result sets is intriguing.

Consider the short script shown below. I'm confused about why the
second SELECT statement returns 1 row, but the first and third
SELECT statements return 0 rows.

Do you understand why this behavior exists, and whether it's appropriate?

ij> create table t (a int, b int);
0 rows inserted/updated/deleted
ij> select sum(b) from t group by a;
1
-----------

0 rows selected
ij> select sum(b) from t;
1
-----------
NULL

1 row selected
ij> insert into t values (1,1);
1 row inserted/updated/deleted
ij> select sum(b) from t where 1 <> 1 group by a;
1
-----------

0 rows selected


> Add support for GROUP BY ROLLUP
> -------------------------------
>
>                 Key: DERBY-3002
>                 URL: https://issues.apache.org/jira/browse/DERBY-3002
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>    Affects Versions: 10.4.1.3
>            Reporter: Bryan Pendleton
>            Assignee: Bryan Pendleton
>            Priority: Minor
>         Attachments: fixWhiteSpace.diff, IncludesASimpleTest.diff, prototypeChangeNoTests.diff, useLookahead.diff
>
>
> Provide an implementation of the ROLLUP form of multi-dimensional grouping according to the SQL standard.
> See http://wiki.apache.org/db-derby/OLAPRollupLists for some more detailed information about this aspect of the SQL standard.

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