U-SQL如何为每个日期选择前3个例外

Question

如何使用U-SQL每天提取前三个例外？

我希望结果看起来像这样：

Answer 1

在U-SQL中实现此目的的一种方法是使用按日期分区的ROW_NUMBER排名函数，并按计数降序排序。例如：

@input = SELECT *
     FROM (
        VALUES
            ( "2016-01-01T00:00:00", "System.ArgumentNullException", 7 ),
            ( "2016-01-01T00:00:00", "System.IO.EndOfStreamException", 5 ),
            ( "2016-01-01T00:00:00", "System.IO.FileNotFoundException", 4 ),
            ( "2016-01-01T00:00:00", "System.IndexOutofRangeException", 4 ),
            ( "2016-01-01T00:00:00", "System.ArgumentException", 3 ),
            ( "2016-01-02T00:00:00", "System.BadImageFormatException", 18 ),
            ( "2016-01-02T00:00:00", "System.IO.EndOfStreamException", 16 ),
            ( "2016-01-02T00:00:00", "System.NotImplementedException", 14 ),
            ( "2016-01-02T00:00:00", "System.UnauthorizedAccessException", 13 ),
            ( "2016-01-02T00:00:00", "System.ArgumentException", 12 ),
            ( "2016-01-02T00:00:00", "System.IndexOutofRangeException", 5 ),
            ( "2016-01-03T00:00:00", "System.IO.EndOfStreamException", 45 ),
            ( "2016-01-03T00:00:00", "System.FormatException", 42 ),
            ( "2016-01-03T00:00:00", "System.BadImageFormatException", 41 ),
            ( "2016-01-03T00:00:00", "System.IndexOutofRangeException", 41 ),
            ( "2016-01-03T00:00:00", "System.IO.FileNotFoundException", 40 )

     ) AS x(date, exception, count);



// Add row number to resultset based on date and count descending
@working =
    SELECT ROW_NUMBER() OVER(PARTITION BY date ORDER BY count DESC) AS rn,
           *
    FROM @input;


// Top 3 by date?
@output =
    SELECT *
    FROM @working
    WHERE rn <= 3;


OUTPUT @output TO "/output/output.csv"
USING Outputters.Csv();

我的结果：