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https://issues.apache.org/jira/browse/DERBY-6103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13617157#comment-13617157
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Dag H. Wanvik commented on DERBY-6103:
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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 (),
giving
ROW_NUMBER () OVER <window name or specification>
then
<window name or specification> -> <window name>
giving
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: 10.10.1.1
> 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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