oracle 排序 row_number() over(partition by 排序字段)

业务描述：按t.truckId,t.riskCode 分组，每个分组里有分数，取分组中分数最大的那条记录。

如：A1 B1   5  6    

      A1  B1   5  3

      A1  B2   2  5

      A1  B2   2  1

已经按 A,B分组了 但是 我需要第一条和第三条数据，就可以用这个row_number() over(partition by  排序字段)降序

然后取 rowseq = 1 的数据就可以拿到了

SELECT
     gg.sumScore     AS sumScore,
     gg.numberRisk   AS numberRisk,
     gg.happenTime   AS happenTime
FROM (
        SELECT
         g.sumScore      AS sumScore,
         g.numberRisk    AS numberRisk,
         g.happenTime    AS happenTime ,

        (row_number() over(partition by g.truckId  order by g.sumScore desc) ) as rowseq --分数最大的排在前面
        FROM(
            SELECT
            sum(score)                    as sumScore  ,--分数
            count(t.riskCode)          as numberRisk ,
            max(t.happenTime)      as  happenTime,
            t.truckId                      as  truckId
            FROM
            (
                SELECT
                    t1.truck_id  truckId,
                    to_char(t1.happen_time,'yyyy-mm-dd hh24:mi:ss')   AS  happenTime,
                    t2.score         As  score,
                    t2.code          As  riskCode
                FROM  b_risk_event t1
                INNER JOIN d_dictionary_info t2 ON t1.risk_type = t2.code
                WHERE t1.happen_time >  SYSDATE-30/(24*60)
                AND t1.del_flag='0'
                AND t2.father_type in('1','2','3','5','8','17','18','0')
                order by t1.happen_time DESC
            ) t
            GROUP BY t.truckId,t.riskCode
            ORDER  BY sumScore DESC,happenTime DESC
        )g
    ) gg

   WHERE   gg.rowseq =1