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https://issues.apache.org/jira/browse/DERBY-2998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523273
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Bryan Pendleton commented on DERBY-2998:
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Thomas, thanks for posting your findings so far. Knowing what doesn't work can
be very useful, and is certainly worth recording. We will all be doing a lot of
learning
about Derby; that's the fun of open source!
Here's a suggestion: perhaps you could investigate how "expressions" are
computed,
by tracing through the compilation and execution of statements such as:
select substring(last_name from 1 for 10) from employee
select case when age < 21 then 'minor' else 'adult' end from dependents
select cost + cost * 0.0825 as cost_including_taxes from sales_history
Can
select row_number(), last_name, emp_id from employee
be modeled in the same fashion?
I agree that eventually we will have to consider the "window" concept to have a
true
implementation of this feature, but perhaps to start we can just build a simple
scalar function that has reasonable behavior for its particular result set, and
see
what we can learn from that prototype implementation.
> Add support for ROW_NUMBER() window function
> --------------------------------------------
>
> Key: DERBY-2998
> URL: https://issues.apache.org/jira/browse/DERBY-2998
> Project: Derby
> Issue Type: Sub-task
> Components: SQL
> Reporter: Thomas Nielsen
> Assignee: Thomas Nielsen
> Priority: Minor
>
> As part of implementing the overall OLAP Operations features of SQL
> (DERBY-581), implement the ROW_NUMBER() window function.
> More information about this feature is available at
> http://wiki.apache.org/db-derby/OLAPRowNumber
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