hive的行列转换进阶之字段名与字段值的互相转换，str

本文列举在一些特殊需求下，比如需要把多行数据根据某一列的字段值转化为字段名的多行转一行的需求，或者把字段名转化为字段值的一行转多行的需求
有点拗口，且看两个实例：

将下表

转化成这样

select name
         ,info['语文'] as Chinese
         ,info['数学'] as Math
         ,info['英语'] as English
  from (select name,str_to_map(concat_ws(',',collect_set(concat_ws(':',subject,cast(score as string))))) as info
          from test
         group by name
             ) a 

select name
      ,max(case when subject = '语文' then score else 0 end) as Chinese
      ,max(case when subject = '数学' then score else 0 end) as Math
      ,max(case when subject = '英语' then score else 0 end) as English
  from test
 group by name

转化成

select a.date
      ,b.label
      ,b.value
  from (select *
          from daily_report
           ) a 
     LATERAL VIEW explode (map(
             'UV', uv
             ,'新增UV', newuv 
             ,'视频存量', video
             ,'新增视频', newvideo
             ,'播放量', vv
             ,'会员数', vip_num
             ,'新增会员数', new_vip_num
               )) b as label, value