Hive 在配置单元中从多行透视到多列

我有一张蜂巢桌，如下所示

(id:int, vals: Map<String, int> , type: string)
id, vals, type
1, {"foo": 1}, "a"
1, {"foo": 2}, "b"
2, {"foo": 3}, "a"
2, {"foo": 1}, "b"

---

如果缺少任何“类型”，它可以为空？

记住

map

列的简单方法是

自连接

select ta.id,ta.vals,tb.vals
from (select * from tbl where type = 'a') ta 
full join (select * from tbl where type = 'b') tb on ta.id = tb.id 

您可以使用条件聚合来解决如下问题。但是，在
映射
列上执行此操作将产生错误

select id
      ,max(case when type = 'a' then vals end) as type_a_vals
      ,max(case when type = 'b' then vals end) as type_a_vals
from tbl
group by id

select id
      ,max(case when type = 'a' then vals end) as type_a_vals
      ,max(case when type = 'b' then vals end) as type_a_vals
from tbl
group by id