[GitHub] flink issue #4556: [FLINK-6465][table]support FIRST_VALUE on Table API & SQL

[sunjincheng121]

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 


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