sql - Bigquery - json_extract 从数组中提取所有元素

Question

我正在尝试从一组 jsons 中的每个 json 中提取两个 key (使用 sql legacy)
目前我正在使用 json 提取功能:

json_extract(json_column , '$[1].X') AS X,
json_extract(json_column , '$[1].Y') AS Y,

我怎样才能让它在'json arry column'的每个json上运行，而不仅仅是[1](例如)？

一个示例 json:

[

{"blabla":000,"X":1,"blabla":000,"blabla":000,"blabla":000,,"Y":"2"},

{"blabla":000,"X":3,"blabla":000,"blabla":000,"blabla":000,,"Y":"4"},

]   

提前致谢!

Answer 1

2020 年更新:JSON_EXTRACT_ARRAY()

BigQuery 现在支持 JSON_EXTRACT_ARRAY() :

https://cloud.google.com/bigquery/docs/reference/standard-sql/json_functions#json_extract_array

例如，要解决这个特定问题:

SELECT id
  , ARRAY(
      SELECT JSON_EXTRACT_SCALAR(x, '$.author.email') 
      FROM UNNEST(JSON_EXTRACT_ARRAY(payload, "$.commits"))x
  ) emails
FROM `githubarchive.day.20180830` 
WHERE type='PushEvent' 
AND id='8188163772'

上一个答案

让我们从一个类似的问题开始——这不是从 json 数组中提取所有电子邮件的非常方便的方法:

SELECT id
  , [ JSON_EXTRACT_SCALAR(JSON_EXTRACT(payload, '$.commits'), '$[0].author.email')  
      , JSON_EXTRACT_SCALAR(JSON_EXTRACT(payload, '$.commits'), '$[1].author.email')  
      , JSON_EXTRACT_SCALAR(JSON_EXTRACT(payload, '$.commits'), '$[2].author.email')  
      , JSON_EXTRACT_SCALAR(JSON_EXTRACT(payload, '$.commits'), '$[3].author.email')
    ] emails
FROM `githubarchive.day.20180830` 
WHERE type='PushEvent' 
AND id='8188163772'

我们现在处理这个问题的最好方法是在 UDF 中使用一些 JavaScript 将 json 数组拆分为 SQL 数组:

CREATE TEMP FUNCTION json2array(json STRING)
RETURNS ARRAY<STRING>
LANGUAGE js AS """
  return JSON.parse(json).map(x=>JSON.stringify(x));
"""; 

SELECT * EXCEPT(array_commits),
  ARRAY(SELECT JSON_EXTRACT_SCALAR(x, '$.author.email') FROM UNNEST(array_commits) x) emails
FROM (
  SELECT id
    , json2array(JSON_EXTRACT(payload, '$.commits')) array_commits
  FROM `githubarchive.day.20180830` 
  WHERE type='PushEvent' 
  AND id='8188163772'
)