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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, 22 Mar 2013 06:47:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609995#comment-13609995

Dag H. Wanvik commented on DERBY-6103:

Actually, the sentence is still correct. The syntax should be improved a bit though:


ROW_NUMBER() OVER window_name WINDOW window_name AS ()


<window function> ::=
     <window function type> OVER <window name or specification>

<window function type> ::=
     ROW_NUMBER <left paren> <right paren>

<window name or specification> ::=
    <window name>
  | <window specification>

<window specification> ::=
    <left paren> <right paren>

<window-name> ::= sql92Identifier

and also in the selectExpression section (rrefselectexpression.html) we should insert:

SELECT [ DISTINCT | ALL ] SelectItem [ , SelectItem ]*
FROM clause
[ WHERE clause ]
[ GROUP BY clause ]
[ HAVING clause ]
[ WINDOW clause ]     <-------------------
[ ORDER BY clause ]
[ result offset clause ]
[ fetch first clause ]

and add

<window clause> ::=
    WINDOW <window-name> <window specification>

Not sure how many sections to make/spread these over....  maybe it
would be good to have a section for <window specification>,
which could be referenced by both the ROW_NUMBER section an the selectExpression section.

This is all a bit premature really, since we don't allow anything except the empty specification
yet, but if we get it right now I should be easy to extend later.

> 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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