Question

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：

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

我怎样才能使其在“ json arry 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"},

]

提前谢谢！

Answer 1

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便捷方法：

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：

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'
)

Answer 2

下面是BigQuery标准SQL的示例，它使您可以接近使用JSONPath的标准方式，并且不需要额外的操作，因此您只需使用CUSTOM_JSON_EXTRACT(json, json_path)函数

#standardSQL
CREATE TEMPORARY FUNCTION CUSTOM_JSON_EXTRACT(json STRING, json_path STRING)
RETURNS ARRAY<STRING>
LANGUAGE js AS """
        return jsonPath(JSON.parse(json), json_path);
"""
OPTIONS (
    library="gs://your_bucket/jsonpath-0.8.0.js"
);
WITH t AS (
SELECT '''
[
{"blabla1":1,"X":1,"blabla2":3,"blabla3":5,"blabla4":7,"Y":"2"},
{"blabla1":2,"X":3,"blabla2":4,"blabla3":6,"blabla4":8,"Y":"4"}
]   
''' AS json_column 
)
SELECT 
  CUSTOM_JSON_EXTRACT(json_column , '$[*].X') AS X,
  CUSTOM_JSON_EXTRACT(json_column , '$[*].Y') AS Y
FROM t

结果将是

Row X   Y    
1   1   2    
    3   4

注意：为克服当前BigQuery对JsonPath的“限制”，上述解决方案使用custom function和external library-jsonpath-0.8.0.js，可以从https://code.google.com/archive/p/jsonpath/downloads下载并上传到Google云端存储-gs：//your_bucket/jsonpath-0.8.0.js

只需重新阅读Felipe的答案-对于他上面的示例，解决方案将如下所示（仅供参考）

SELECT 
  id, 
  CUSTOM_JSON_EXTRACT(payload, '$.commits[*].author.email') emails
FROM `githubarchive.day.20180830` 
WHERE type='PushEvent' 
AND id='8188163772'

BigQuery-json_extract数组中的所有元素

2 个答案: