在雪花中对 JSON 使用横向扁平化答案

【问题标题】：Use of Lateral Flatten for JSON in Snowflake在雪花中对 JSON 使用横向扁平化
【发布时间】：2022-08-20 02:25:13
【问题描述】：

我有以下 JSON 作为雪花中的变体字段。查询数据时我得到NULLS，如下所示 - -

create or replace table car_sales
( 
  src variant
)
as
select parse_json(column1) as src
from values
(\'{
  \"MyData\": {
    \"DataID\": \"16784\",
    \"EmpFirstName\": \"Jenny\",
    \"EmpLastName\": \"Test1\",
    \"Description\": \"My Company Data\",
    \"Assignment\": [
      {
        \"AssignentId\": \"1077\",
        \"AssignentName\": \"Multi Location\",
        \"AssignentDescription\": \"usa\",
      },
    ],
    \"salary\": 21557
  },
  \"Update\": true
}\') v;

当我查询数据时，我得到 Nulls -

select value:AssignentId::string as \"1ProductName\"
from car_sales,
lateral flatten(input => src:Assignment);

输出为 NULL

您能帮助解决为什么会发生这种情况吗？

标签： json snowflake-cloud-data-platform

【解决方案1】：

尝试添加我的数据横向展平中的限定符：

with car_sales(src) as (
    select
        parse_json(column1) as src
    from
    values
        (
            '{ "MyData": {
     "DataID": "16784",
    "EmpFirstName": "Jenny",
    "EmpLastName": "Test1",
    "Description": "My Company Data",
    "Assignment": [
      {
        "AssignentId": "1077",
        "AssignentName": "Multi Location",
        "AssignentDescription": "usa",
      },
    ],
    "salary": 21557
    }, "Update": true }'
        )
)
select
    value:AssignentId::string as "1ProductName"
from
    car_sales,
    lateral flatten(input => src:MyData:Assignment);

1ProductName
1077

【讨论】：

【解决方案2】：

您正在尝试直接访问子节点。同时指定父节点

select value:AssignentId::string as "1ProductName"
from car_sales,
lateral flatten(input => src:MyData:Assignment);

input => src:Assignment

应该

input => src:MyData:Assignment

这是读取每个键的值的查询

select  src:MyData.DataID::string as "DataID"
        , src:MyData.EmpFirstName::string as "EmpFirstName"
        , src:MyData.EmpLastName::string as "EmpLastName"
        , src:MyData.Description::string as "Description"
        , src:MyData.Assignment[0]:AssignentId::string as "AssignentId/1ProductName"
        , src:MyData.Assignment[0]:AssignentName::string as "AssignentName"
        , src:MyData.Assignment[0]:AssignentDescription::string as "AssignentDescription"
        , src:MyData.salary::number as "salary"
        , src:Update::boolean as "Update"
from car_sales

【讨论】：

如何在我的查询中添加其他标签，如更新。例如从 car_sales 中选择 value.Update::Boolean 作为“Update”，value:AssignentId::string 作为“1ProductName”，横向展平（input => src:MyData:Assignment）；以上查询给了我一个错误 - 意外的“更新”。