hive 多列转单行

原表数据如下,业务场景是取用户的top5站点访问情况，行号是根据访问次数降序生成。
用户ID  | 站点名   |  流量   |访问次数  |行号
user_id |site_name |all_flow |net_times |rn
1          a           10         5       1
1          b           23         4       2
1          c           56         3       3
1          d           12         2       4
1          e           14         1       5
下一步需求是将多列转为单行，如下
user_id|top1_name|top1_times|top1_flow|top2_name|top2_times|top2_flow|top3_name|top3_times|top3_flow|top4_name|top4_times|top4_flow|top5_name|top5_times|top5_flow
1|a|5|10|b|4|23|c|3|56|d|2|12|e|1|14
转换代码：
SELECT USER_ID,
         MAX(CASE WHEN RN = 1 THEN SITE_NAME END) AS TOP1_NAME,
         SUM(CASE WHEN RN = 1 THEN NET_TIMES ELSE CAST( '0' AS BIGINT) END) AS TOP1_TIMES,
         SUM(CASE WHEN RN = 1 THEN ALLFLOW ELSE CAST( '0' AS BIGINT) END) AS TOP1_FLOW,
         MAX(CASE WHEN RN = 2 THEN SITE_NAME END) AS TOP2_NAME,
         SUM(CASE WHEN RN = 2 THEN NET_TIMES ELSE CAST( '0' AS BIGINT) END) AS TOP2_TIMES,
         SUM(CASE WHEN RN = 2 THEN ALLFLOW ELSE CAST( '0' AS BIGINT) END) AS top2_flow,
         MAX(CASE WHEN RN = 3 THEN SITE_NAME END) AS TOP3_NAME,
         SUM(CASE WHEN RN = 3 THEN NET_TIMES ELSE CAST( '0' AS BIGINT) END) AS top3_times,
         SUM(CASE WHEN RN = 3 THEN ALLFLOW ELSE CAST( '0' AS BIGINT) END) AS top3_flow,
         MAX(CASE WHEN RN = 4 THEN SITE_NAME END) AS TOP4_NAME,
         SUM(CASE WHEN RN = 4 THEN NET_TIMES ELSE CAST( '0' AS BIGINT) END) AS top4_times,
         SUM(CASE WHEN RN = 4 THEN ALLFLOW ELSE CAST( '0' AS BIGINT) END) AS top4_flow,
         MAX(CASE WHEN RN = 5 THEN SITE_NAME END) AS TOP5_NAME,
         SUM(CASE WHEN RN = 5 THEN NET_TIMES ELSE CAST( '0' AS BIGINT) END) AS top5_times,
         SUM(CASE WHEN RN = 5 THEN ALLFLOW ELSE CAST( '0' AS BIGINT) END) AS top5_flow
   FROM ... where ...
   GROUP BY USER_ID ORDER BY USER_ID DESC;