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https://issues.apache.org/jira/browse/DERBY-3002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749974#action_12749974
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Dag H. Wanvik commented on DERBY-3002:
--------------------------------------
Playing with the latest patch, I notice something that puzzles me (totally
contrived example :-) :
> describe t;
COLUMN_NAME |TYPE_NAME|DEC&|NUM&|COLUM&|COLUMN_DEF|CHAR_OCTE&|IS_NULL&
------------------------------------------------------------------------------
C |VARCHAR |NULL|NULL|2 |NULL |4 |NO
C2 |VARCHAR |NULL|NULL|2 |NULL |4 |YES
I |INTEGER |0 |10 |10 |NULL |NULL |YES
with a few columns:
> select * from t
C |C2 |I
-------------------
aa|NULL|NULL
bb|NULL|NULL
Then I try this:
> select c,c2,sum(i) from t group by rollup (c,c2)
and I see:
C |C2 |3
---------------------
aa |NULL|NULL
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
aa |NULL|NULL
NULL|NULL|NULL
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
bb |NULL|NULL
bb |NULL|NULL
which is I think is as expected. But then I tried:
ij> select cast(c as varchar(2)),c2,sum(i) from t group by rollup (c,c2)
but now I see:
1 |C2 |3
---------------------
aa |NULL|NULL
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
aa |NULL|NULL
bb |NULL|NULL
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
bb |NULL|NULL
bb |NULL|NULL
Notice that the third row is now different (equal to row four). Is this correct?
If I embed this group by into a subquery:
ij> select cast(x as varchar(2)),y,z from (select c,c2,sum(i) from t group by
rollup (c,c2)) t(x,y,z)
I see again the row with null, null, null:
1 |Y |Z
-------------------
aa|NULL|NULL
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
aa|NULL|NULL
N&|NULL|NULL
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
WARNING 01003: Null values were eliminated from the argument of a column
function.
bb|NULL|NULL
bb|NULL|NULL
but this time, the nullability of column 1 seems wrong (notice the
"N&" - ij will use two columns here (VARCHAR(2)) if it thinks column can't
contain
a NULL which, of course, needs 4 columns to print). This could be
related to the problem Knut is working on under DERBY-4284, though.
> Add support for GROUP BY ROLLUP
> -------------------------------
>
> Key: DERBY-3002
> URL: https://issues.apache.org/jira/browse/DERBY-3002
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.4.1.3
> Reporter: Bryan Pendleton
> Assignee: Bryan Pendleton
> Priority: Minor
> Attachments: fixWhiteSpace.diff, IncludesASimpleTest.diff,
> passesRegressionTests.diff, prototypeChangeNoTests.diff,
> rewriteGroupByRS.diff, rollupNullability.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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