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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3634) Cannot use row_number() in ORDER BY clause
Date Thu, 08 Oct 2009 00:31:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12763317#action_12763317

Dag H. Wanvik commented on DERBY-3634:

Some comments on your cases, Knut.

ij> values row_number() over ();

This should be flagged. SQL 2003, section 4.14.9 Windowed tables says:
"A window is a transient data structure associated with a <table
expression>."  A window function like ROW_NUMBER is always defined
relative a window, and there is no <table expression> here and hence
no window either.

Explicitly, in 4.15.3: Window functions may only appear in the <select
list> of a <query specification> or <select statement: single row>, or
the <order by clause> of a simple table query.

ij> select * from t where exists (select row_number() over () from t);


ij> select * from t where row_number() over () > 3;

Should be flagged, cf. 4.15.3 quoted above.

ij> select row_number() over (), count(*) from t group by row_number() over ();
ij> select count(*) from t group by row_number() over ();

Both should be flagged, GROUP BY allows <ordinary grouping set> ->
<grouping column reference>. Cf. 4.15.3 quoted above as well.

> Cannot use row_number() in ORDER BY clause
> ------------------------------------------
>                 Key: DERBY-3634
>                 URL: https://issues.apache.org/jira/browse/DERBY-3634
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions:
>            Reporter: Rick Hillegas
>            Assignee: Dag H. Wanvik
>         Attachments: derby-3634-a.diff, derby-3634-a.stat, derby-3634-a.txt, derby-3634-b.diff,
derby-3634-b.stat, derby-3634-c.diff, derby-3634-c.stat, derby-3634-newimpl-1.diff, derby-3634-newimpl-1.stat,
derby-3634-newimpl-1.txt, derby-3634-newimpl-2.diff, derby-3634-newimpl-2.stat, derby-3634-remove-2.diff,
derby-3634-remove-2.stat, derby-3634-remove.diff, derby-3634-remove.stat
> The following query works correctly:
> select abs(a), row_number() over ()
> from t
> where a > 100 and a < 111
> order by abs(a)
> I expected the following query to also work, but it raised an exception:
> select abs(a), row_number() over ()
> from t
> where a > 100 and a < 111
> order by row_number() over ()
> This is the error I saw: "ERROR 42X01: Syntax error: Encountered "over" at line 5, column
> Here are the reasons why I think that this syntax is supposed to be supported:
> According to my reading of the 2003 SQL spec, the ORDER BY clause should be able to sort
on any expression in the SELECT list. That includes OLAP expressions. I believe this is so
because, according to part 2, section 10.10 (<sort specification>), a <sort key>
can be any <value expression> and if you follow the grammar for <value expression>,
it can resolve to be a <value expression primary> (see section 6.3), which can in turn
resolve to be a <window function>. This reasoning is supported by tracing the hotlinks
on the following page which lays out the SQL 2003 BNF: http://savage.net.au/SQL/sql-2003-2.bnf.html
This interpretation is further supported by the example of an ORDER BY clause referencing
an OLAP expression which is provided on page 23 of the introduction to OLAP written by Fred
Zemke, Krishna Kulkarni, Andy Witkowski, and Bob Lyle: www.cse.iitb.ac.in/dbms/Data/Papers-Other/SQL1999/OLAP-99-154r2.pdf

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