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https://issues.apache.org/jira/browse/FLINK-6228?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15956904#comment-15956904
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Fabian Hueske commented on FLINK-6228:
--------------------------------------

I'm not sure whether each window type is useful / required for both {{groupBy}} 
and {{over}}.

How would an {{OverWindow}} be defined? What would be the semantics of an 
{{OverWindow}} with {{groupBy}}?
Also {{OverWindow}} (as in SQL) can express the semantics that I have in mind 
for {{TumbleWindow}} and {{SlideWindow}} for {{over}}. Hence, {{TumbleWindow}} 
and {{SlideWindow}} would just be syntactic sugar and not add to expressiveness.
I agree that {{SessionWindow}} would be useful for {{over}} as well.

> Integrating the OVER windows in the Table API
> ---------------------------------------------
>
>                 Key: FLINK-6228
>                 URL: https://issues.apache.org/jira/browse/FLINK-6228
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>            Reporter: sunjincheng
>            Assignee: sunjincheng
>
> Syntax:
> {code}
> table
>    .overWindows(
>     (Rows|Range [ partitionBy value_expression , ... [ n ]] [ orderBy 
> order_by_expression] 
>       (preceding  
> UNBOUNDED|value_specification.(rows|milli|second|minute|hour|day|month|year)|CURRENTROW)
>      [following 
> UNBOUNDED|value_specification.(rows|milli|second|minute|hour|day|month|year)|CURRENTROW]
>     as alias,...[n])
>    )
>   .select( [col1,...[n]], (agg(col1) OVER overWindowAlias, … [n])
> {code}
> Implement restrictions:
> * All OVER clauses in the same SELECT clause must be exactly the same.
> * The PARTITION BY clause is optional (no partitioning results in single 
> threaded execution).
> * The ORDER BY Before the 
> [FLINK-5884|https://issues.apache.org/jira/browse/FLINK-5884]  implementation 
> orderBy may only have ‘rowtime/’proctime(for stream)/‘specific-time-field(for 
> batch).
> * FOLLOWING is not supported.
> I will soon add a user interface design document.



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