将 JSON 加载到 BigQuery:字段有时是数组,有时是字符串
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【中文标题】将 JSON 加载到 BigQuery:字段有时是数组,有时是字符串【英文标题】:Loading JSON into BigQuery: Field is sometimes an array and sometimes a string 【发布时间】:2020-12-30 16:05:49 【问题描述】:我正在尝试将 JSON 数据加载到 BigQuery。我的数据导致问题的摘录如下所示:
["Value":"123","Code":"A","Value":"000","Code":"B"]
"Value":"456","Code":"A"
["Value":"123","Code":"A","Value":"789","Code":"C","Value":"000","Code":"B"]
"Value":"Z","Code":"A"
我已将此字段的架构定义为:
"fields": [
"mode": "NULLABLE",
"name": "Code",
"type": "STRING"
,
"mode": "NULLABLE",
"name": "Value",
"type": "STRING"
],
"mode": "REPEATED",
"name": "Properties",
"type": "RECORD"
但我无法成功地将字符串和数组值提取到一个重复字段中。此 SQL 将成功提取字符串值:
JSON_EXTRACT_SCALAR(json_string,'$.Properties.Code') as Code,
JSON_EXTRACT_SCALAR(json_string,'$.Properties.Value') as Value
并且这条 SQL 将成功提取数组值:
ARRAY(
SELECT
STRUCT(
JSON_EXTRACT_SCALAR(Properties_Array,'$.Code') AS Code,
JSON_EXTRACT_SCALAR(Properties_Array,'$.Value') AS Value
)
FROM UNNEST(JSON_EXTRACT_ARRAY(json_string,'$.Properties')) Properties_Array)
AS Properties
我正在尝试找到一种方法让 BigQuery 将此字符串作为单元素数组读取,而不是对数据进行预处理。这在#StandardSQL 中可行吗?
【问题讨论】:
【参考方案1】:以下示例适用于 BigQuery 标准 SQL
#standardSQL
WITH `project.dataset.table` as (
SELECT '"Properties":["Value":"123","Code":"A","Value":"000","Code":"B"]' json_string UNION ALL
SELECT '"Properties":"Value":"456","Code":"A"' UNION ALL
SELECT '"Properties":["Value":"123","Code":"A","Value":"789","Code":"C","Value":"000","Code":"B"]' UNION ALL
SELECT '"Properties": "Value":"Z","Code":"A"'
)
SELECT json_string,
ARRAY(
SELECT STRUCT(
JSON_EXTRACT_SCALAR(Properties,'$.Code') AS Code,
JSON_EXTRACT_SCALAR(Properties,'$.Value') AS Value
)
FROM UNNEST(IFNULL(
JSON_EXTRACT_ARRAY(json_string,'$.Properties'),
[JSON_EXTRACT(json_string,'$.Properties')])) Properties
) AS Properties
FROM `project.dataset.table`
有输出
【讨论】:
非常感谢@mikhail-berlyant!像魅力一样工作。我尝试了几种 UDF、CASE 语句和 CTE 的组合,并预感到解决方案将涉及检查空数组。以上是关于将 JSON 加载到 BigQuery:字段有时是数组,有时是字符串的主要内容,如果未能解决你的问题,请参考以下文章
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