BigQuery-json_extract数组中的所有元素 [英] Bigquery - json_extract all elements from an array

问题描述

我正在尝试从json中提取每个json中的两个密钥(使用sql legacy) 目前，我正在使用json提取功能:

i'm trying to extract two key from every json in an arry of jsons(using sql legacy) currently i am using json extract function :

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

我如何才能使其在"json arry列"的每个json上运行，而不仅仅是[1](例如)?

how can i make it run on every json at the 'json arry column', and not just [1] (for example)?

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"},

]   

提前谢谢！

推荐答案

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

Let's start with a similar problem - this is not a very convenient way to extract all emails from a json array:

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'

我们现在要解决的最佳方法是在UDF中使用一些JavaScript将json数组拆分为SQL数组:

The best way we have right now to deal with this is to use some JavaScript in an UDF to split a json-array into a SQL array:

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'
)

这篇关于BigQuery-json_extract数组中的所有元素的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！