攤平半結構化資料

Snowflake 的資料型別與函式

Jake Roach

Field Data Engineer

結構化資料

     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
                |        }
                |    }

半結構化資料

以大括號包住的鍵值配對會使用 VARIANT 型別儲存

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

類似 Python 字典或 JSON 物件
允許以「原始」格式儲存資料
可巢狀物件，如 address
有兩種方式可擷取資料

點記法（Dot-notation）

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

SELECT

    my_column:my_first_key         -- Top-level

    my_column:my_second_key.a   -- Nested
    my_column:my_second_key.b   -- Nested

...

讓你能輕鬆從 VARIANT 擷取頂層與巢狀值

冒號分隔 <column-name>:<top-level-key>
加上 . 與巢狀欄位：<column-name>:<top-level-key>.<nested-key>
可擷取更深層的巢狀值

點記法（Dot-notation）

SELECT
    address_info:school_name,                              -- Top-level, dot-notation

    address_info:address.street_number AS street_number,   -- Nested, dot-notation
    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.

中括號記法（Bracket-notation）

提供另一種擷取頂層與巢狀值的技巧

<column-name>['<top-level-key']['...']
可有多層巢狀
類似從 Python 字典取值
務必使用「單引號（'）」！

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

SELECT

    my_column['my_first_key'],       -- Top-level

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

...

中括號記法（Bracket-notation）

SELECT

    address_info['school_name'],                      -- Top-level, bracket-notation


    address_info['address']['city'] AS city,           -- Nested, bracket-notation
    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

轉換半結構化資料

SELECT
    school_id,

    address_info:school_name AS school_name,               -- Top-level, dot-notation

    address_info:address.street_number AS street_number,   -- Nested, dot-notation
    address_info:address.street_name AS street_name,
    address_info:address.suffix AS suffix,

    address_info['address']['city'] AS city,               -- Nested, bracket-notation
    address_info['address']['zip_code'] AS zip_code

FROM SCHOOLS.school_info;

轉換半結構化資料

     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

一起來練習吧！

Snowflake 的資料型別與函式