展平半结构化数据

Snowflake 中的数据类型与函数

Jake Roach

Field Data Engineer

结构化数据

     school_id  |    school_name    |  street_number  |  street_name  |  suffix   |      city      |  zip_code
    ----------- | ----------------- | --------------- | ------------- | --------- | -------------- | ----------
      s_19219   |  West Aurora HS   |       879       |    Main       |    St.    |  West Aurora   |   25041
      s_77465   |  Springtown HS    |      1645       |    Cherry     |    Rd.    |  Springtown    |   14556

     school_id  |                address_info        
    ----------- | ------------------------------------------
      s_19219   |    {
                |        "school_name": "West Aurora HS",
                |        "address": {
                |            "street_number": 879,
                |            "street_name": "Main",
                |            "suffix":  "St."
                |            "city": "West Aurora",
                |            "zip_code": 25041
                |        }
                |    }

半结构化数据

用花括号存储的键值对数据，数据类型为 VARIANT

{
    "school_name": "West Aurora HS",
    "address": {  -- 嵌套对象
        "street_number": 879,
        "street_name": "Main",
        "suffix": "St.",
        "city": "West Aurora",
        "zip_code": 25041
    }
}

类似 Python 字典或 JSON 对象
允许以"原始"格式存储数据
可嵌套对象，如 address
有两种检索方式

点表示法

                  my_column  
 -------------------------------------------
        {
            "my_first_key": 2025,
            "my_second_key": {
                "a": "alpha",
                "b": "bravo"
            }
        }

SELECT

    my_column:my_first_key         -- 顶层

    my_column:my_second_key.a   -- 嵌套
    my_column:my_second_key.b   -- 嵌套

...

便于从 VARIANT 数据中检索顶层和嵌套值

冒号分隔 <column-name>:<top-level-key>
追加 . 与嵌套字段 <column-name>:<top-level-key>.<nested-key>
支持深层嵌套取值

点表示法

SELECT
    address_info:school_name,                              -- 顶层，点表示法

    address_info:address.street_number AS street_number,   -- 嵌套，点表示法
    address_info:address.street_name AS street_name,
    address_info:address.suffix AS suffix

FROM SCHOOLS.school_info;

              school_name    |  street_number  |  street_name  |  suffix  
           ----------------- | --------------- | ------------- | ---------
            West Aurora HS   |       879       |    Main       |    St.   
            Springtown HS    |      1645       |    Cherry     |    Rd.

方括号表示法

提供另一种检索顶层与嵌套值的方法

<column-name>['<top-level-key']['...']
支持多层嵌套
类似从 Python 字典取值
请务必使用单引号（'）！

                    my_column  
 ------------------------------------------------
          {
              "my_first_key": 2025,
               my_second_key": {
                  "a": "alpha",
                  "b": "bravo"
              }
          }

SELECT

    my_column['my_first_key'],       -- 顶层

    my_column['my_second_key']['a']   -- 嵌套
    my_column['my_second_key']['b']   -- 嵌套

...

方括号表示法

SELECT

    address_info['school_name'],                      -- 顶层，方括号表示法


    address_info['address']['city'] AS city,           -- 嵌套，方括号表示法
    address_info['address']['zip_code'] AS zip_code


FROM SCHOOLS.school_info;

                     school_name    |      city      |  zip_code
                  ----------------- | -------------- | ----------
                   West Aurora HS   |  West Aurora   |   25041
                   Springtown HS    |  Springtown    |   14556

转换半结构化数据

SELECT
    school_id,

    address_info:school_name AS school_name,               -- 顶层，点表示法

    address_info:address.street_number AS street_number,   -- 嵌套，点表示法
    address_info:address.street_name AS street_name,
    address_info:address.suffix AS suffix,

    address_info['address']['city'] AS city,               -- 嵌套，方括号表示法
    address_info['address']['zip_code'] AS zip_code

FROM SCHOOLS.school_info;

转换半结构化数据

     school_id  |                address_info        
    ----------- | ------------------------------------------
      s_19219   |    {
                |        "school_name": "West Aurora HS",
                |        "address": {
                |            "street_number": 879,
                |            "street_name": "Main",
                |            "suffix":  "St."
                |            "city": "West Aurora",
                |            "zip_code": 25041
                |        }
                |    }

     school_id  |    school_name    |  street_number  |  street_name  |  suffix   |      city      |  zip_code
    ----------- | ----------------- | --------------- | ------------- | --------- | -------------- | ----------
      s_19219   |  West Aurora HS   |       879       |    Main       |    St.    |  West Aurora   |   25041
      s_77465   |  Springtown HS    |      1645       |    Cherry     |    Rd.    |  Springtown    |   14556

Vamos praticar!

Snowflake 中的数据类型与函数