Presto-提取数组中的键

Question

我有这个样本数据（来自雅典娜）

 SELECT DISTINCT m.key
  FROM (VALUES JSON '{"name":"project1","completed":false}', JSON '{"name":"project1","completed":false}',JSON '{"name":"project1","completed":false}')
     example_table(json_column)
 CROSS JOIN UNNEST (map_keys(CAST(json_column AS map<varchar,json>))) AS m(key);

 WITH dataset AS (
  SELECT '{"name": "Susan Smith",
           "org": "engineering",
           "projects": [{"name":"project1", "completed":false},
           {"name":"project2", "completed":true}]}'
    AS blob
)
select * from dataset

这将生成以下输出。

{"name": "Susan Smith", "org": "engineering", "projects": [{"name":"project1", "completed":false}, {"name":"project2", "completed":true}]}

我想从输出中提取Key。

预期产量：

output
------
name
org
projects

有人可以帮忙吗？

更新：

使用正确的JSON编辑了此问题。

Answer 1

根据评论中的讨论，

map_keys(CAST(json_column AS map<varchar,json>))

需要替换为

map_keys(CAST(CAST(json_column AS JSON) AS map<varchar,json>))