使用 HIVE LATERAL VIEW 选择不存在的数据为空

Question

我正在尝试使用蜂巢中的外部爆炸将不存在的数据设为空，但我的查询没有返回任何内容。 编辑 ： 表 - 年份字符串，公司排名

year:string,topcompanies:array<struct<name:string,rank:string>>

样本数据 编辑：

    2015,
  "topcompanies":[
  {"name":"apple","rank":"1"},
  {"name":"samsung","rank":"2"},
  {"name":"SONY","rank":"3"},
  ]

  2016,
  "topcompanies":[
  {"name":"apple","rank":"1"},
  {"name":"samsung","rank":"2"},
  {"name":"SONY","rank":"3"},
  {"name":"LG","rank":"4"}
  ]

查询获取数据

select  year, rank1, rank2, rank3, rank4
FROM companyrank
LATERAL VIEW outer explode(topcompanies) rank1_t as rank1_v
LATERAL VIEW outer explode(topcompanies) rank2_t as rank2_v
LATERAL VIEW outer explode(topcompanies) rank3_t as rank3_v
LATERAL VIEW outer explode(topcompanies) rank4_t as rank4_v
WHERE 
 (rank1_v.rank = 1 or rank1_v.rank is null)
 AND (rank2_v.rank = 2 or rank2_v.rank is null)
 AND (rank3_v.rank = 3 or rank3_v.rank is null)
 AND (rank4_v.rank = 4 or rank4_v.rank is null)

预期输出-

expected output when rank4 does not exists
year  rank1 rank2   rank3   rank4
2016  apple samsung SONY    null

如果rank4数据存在则

    year rank1  rank2   rank3   rank4
    2015 apple  samsung SONY    LG

编辑：

我需要获得每年的所有 4 个排名，如果任何一个排名不存在，那么排名应该显示为 NULL。

Answer 1

您的问题的直接答案是“使用lateral view outer”，但有一个更简洁的解决方案。

select      min (case when i.rank = 1 then i.name end)  as rank1
           ,min (case when i.rank = 2 then i.name end)  as rank2
           ,min (case when i.rank = 3 then i.name end)  as rank3
           ,min (case when i.rank = 4 then i.name end)  as rank4

from        companyrank c
            lateral view inline(topcompanies) i
;

---

+--------+----------+--------+--------+
| rank1  |  rank2   | rank3  | rank4  |
+--------+----------+--------+--------+
| apple  | samsung  | SONY   | NULL   |
+--------+----------+--------+--------+