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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6103) Improve documentation of ROW_NUMBER function
Date Fri, 29 Mar 2013 07:11:24 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13617157#comment-13617157

Dag H. Wanvik commented on DERBY-6103:

That is correct. Currently, we do not allow any other <window specification> than (
), but hopefulyl we will in the future.

But we do allows the window to be specified in two locations, either 1) inline, corresponding
the the first production above ("ROW_NUMBER() OVER ()") , or 2) as part of WINDOW clause shows
with the selectExpression above (needs adding).

The derivation for the other example "ROW_NUMBER() OVER window_name" is 

   <window function> -> <window function type> OVER <window name or specification>
   <window function type> -> ROW_NUMBER OVER <left paren> <right paren>
-> ROW_NUMBER (), 


   ROW_NUMBER () OVER <window name or specification>


   <window name or specification> -> <window name>


   ROW_NUMBER () OVER <window name>

In this case, there is no window specification involved, so the <window name> must refer
to a <window name> introduced by a WINDOW clause. Note that WINDOW clause is *not* part
of the <window function>'s syntax but rather part of the syntax for <selectExpression>.
Hope this helps :)

> Improve documentation of ROW_NUMBER function
> --------------------------------------------
>                 Key: DERBY-6103
>                 URL: https://issues.apache.org/jira/browse/DERBY-6103
>             Project: Derby
>          Issue Type: Improvement
>          Components: Documentation
>    Affects Versions:
>            Reporter: Dag H. Wanvik
>            Assignee: Kim Haase
>            Priority: Minor
>         Attachments: DERBY-6103.diff, DERBY-6103.stat, DERBY-6103.zip
> The current documentation doesn't mention that we allow the window definition to be explicit.
> The restriction on WHERE clause no longer applies, nor does the sentence about ORDER
BY not being allowed in subqueries. Cf. rreffuncrownumber.dita. Also, the documentation mentions
that we don't support LIMIT, but not that we now support the FETCH/OFFSET clause, which is
often a better option than ROW_NUMBER.

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