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https://issues.apache.org/jira/browse/FLINK-6465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16178061#comment-16178061
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ASF GitHub Bot commented on FLINK-6465:
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Github user sunjincheng121 commented on the issue:
https://github.com/apache/flink/pull/4556
I have update the PP. Please look at the PR. :) @fhueske @twalthr @wuchong
@shaoxuan-wang
> support FIRST_VALUE on Table API & SQL
> --------------------------------------
>
> Key: FLINK-6465
> URL: https://issues.apache.org/jira/browse/FLINK-6465
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Hequn Cheng
> Assignee: sunjincheng
>
> {{FIRST_VALUE}} is a OVER WINDOW function. In this JIRA. will add
> {{FIRST_VALUE}} function support on TableAPI & SQL.
> *Syntax:*
> FIRST_VALUE ( [scalar_expression ] )
> OVER ( [ partition_by_clause ] order_by_clause [ rows_range_clause ] )
> [About OVER
> WINDOWS|https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/table/tableApi.html#over-windows]
> scalar_expression
> Is the value to be returned. scalar_expression can be a column, or other
> arbitrary expression that results in a single value. Other analytic functions
> are not permitted.
> *NOTE:*
> * {{FIRST_VALUE}} if used for OVER WINDOW, e.g.:
> {code}
> SELECT A, B, FIRST_VALUE(C) OVER (ORDER BY E) AS firstValue FROM tab
> {code}
> * OVER WINDOW's retraction is expensive(currently not supported yet), and
> this JIRA. does not implement Retract logic of {{FIRST_VALUE}}.
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