arrays - 如何取消嵌套 JSON 数据对象并使用 Snowflake 创建简化的 JSON？

Question

我当前的 JSON 对象如下所示:

-- create a sample table
create or replace table json_example(v variant);
-- create sample json record
insert into json_example
select parse_json(
    '[
      {
        "key": "variable_a",
        "value": {
          "double_value": null,
          "float_value": null,
          "int_value": null,
          "string_value": "https://example.com"
        }
      },
      {
        "key": "variable_b",
        "value": {
          "double_value": null,
          "float_value": null,
          "int_value": 2,
          "string_value": null
        }
      }
     ]');

这是我想要实现的简化 JSON:

  {
    "variable_a": "https://example.com",
    "variable_b": 2
  }

如何从多级 JSON 对象中获取简化的 JSON？

这就是我开始思考的方式:

select value:key::string as key, value:value:string_value::varchar as value
from json_example, lateral flatten(input => v)
union all
select value:key::string as key, value:value:int_value::varchar as value
from json_example, lateral flatten(input => v)

提前谢谢您。

Answer 1

因此，如果您希望所有内容都是 JSON 文本，您可以:

WITH data as (
select parse_json(
    '[
      {
        "key": "variable_a",
        "value": {
          "double_value": null,
          "float_value": null,
          "int_value": null,
          "string_value": "https://example.com"
        }
      },
      {
        "key": "variable_b",
        "value": {
          "double_value": null,
          "float_value": null,
          "int_value": 2,
          "string_value": null
        }
      }
     ]') as json
)
SELECT f.value:key::text as t_key
    ,try_to_double(f.value:value:double_value::text) as d_val
    ,try_to_double(f.value:value:float_value::text) as f_val
    ,try_to_number(f.value:value:int_value::text) as n_val
    ,f.value:value:string_value::text as s_val
    ,coalesce(d_val::text, f_val::text, n_val::text, s_val) as c_val
    ,object_construct(t_key, c_val) as obj
FROM DATA, lateral flatten(input=>json) f

<表类=“s-表”> <标题> T_KEY D_VAL F_VAL N_VAL S_VAL C_VAL OBJ <正文> 变量_a https://example.com https://example.com 变量_b 2 2

然后向我们展示如何构建 CASE 语句，并构建干净的 native 对象，例如:

SELECT 
    case 
        when not is_null_value(f.value:value:double_value) 
            then object_construct(f.value:key::text, try_to_double(f.value:value:double_value::text))
        when not is_null_value(f.value:value:float_value) 
            then object_construct(f.value:key::text, try_to_double(f.value:value:float_value::text))
        when not is_null_value(f.value:value:int_value) 
            then object_construct(f.value:key::text, try_to_number(f.value:value:int_value::text))
        else 
            object_construct(f.value:key::text, f.value:value:string_value::text)
    end obj
FROM DATA, lateral flatten(input=>json) f

<表类=“s-表”> <标题> OBJ <正文> {“variable_a”:“https://example.com”} {“variable_b”:2}

可以将其变成单个对象，如下所示:

SELECT 
    object_agg(f.value:key, 
    case 
        when not is_null_value(f.value:value:double_value) 
            then try_to_double(f.value:value:double_value::text)
        when not is_null_value(f.value:value:float_value) 
            then try_to_double(f.value:value:float_value::text)
        when not is_null_value(f.value:value:int_value) 
            then try_to_number(f.value:value:int_value::text)
        else 
            f.value:value:string_value
    end
   ) as obj
FROM DATA, lateral flatten(input=>json) f

<表类=“s-表”> <标题> OBJ <正文> {“variable_a”:“https://example.com”，“variable_b”:2 }