BigQuery-从一组Json文件中提取数据 [英] BigQuery - Extract data from an array of Json files

问题描述

早上好

在大查询中，我有一个表格，其中的一列具有以下形式(我显示3行):

In big query I have a table with one column on the following form (I show 3 lines):

[{'a':1，'b':4，'c':5}，{'a':0，'b':7，'c':8}，{'a':4，'b':9，'c':12}]

[{'a':9，'b':10，'c':9}]

[{'a':5，'b':10，'c':9}，{'a':1，'b':10，'c':9}，{'a':7，'b':10，'c':9}]

也就是说，我有一个Jsons数组(长度不固定).对于要提取的每一行(创建新列)，如果存在，则当键"a" = 1时键"b"的值(对于每一行，键"a"可以等于1一度).我无法导入外部程序包.

that is, I have an array (Not fixed length) of Jsons. For every row I would like to extract (create a new column), if it is present, the value of the key 'b' when the key 'a'=1 (for every row the key 'a' can be equal 1 just one time). I can not import external packages.

谢谢您的帮助！

推荐答案

以下是BigQuery标准SQL

Below is for BigQuery Standard SQL

#standardSQL
CREATE TEMP FUNCTION json2array(json STRING)
RETURNS ARRAY<STRING>
LANGUAGE js AS """
  return JSON.parse(json).map(x=>JSON.stringify(x));
"""; 
WITH `project.dataset.table` AS (
  SELECT "[{'a':1,'b':4, 'c':5}, {'a':0,'b':7, 'c':8},{'a':4,'b':9, 'c':12}]" json UNION ALL
  SELECT "[{'a':9,'b':10, 'c':9}]" UNION ALL
  SELECT "[{ 'a':5,'b':10, 'c':9}, {'a':1,'b':10, 'c':9}, {'a':7,'b':10, 'c':9}]"
)
SELECT json, JSON_EXTRACT_SCALAR(x, '$.b') AS b
FROM `project.dataset.table`,
  UNNEST(json2array(JSON_EXTRACT(json, '$'))) x
WHERE JSON_EXTRACT_SCALAR(x, '$.a') = '1'

有结果

Row json                                                                        b    
1   [{'a':1,'b':4, 'c':5}, {'a':0,'b':7, 'c':8},{'a':4,'b':9, 'c':12}]          4    
2   [{ 'a':5,'b':10, 'c':9}, {'a':1,'b':10, 'c':9}, {'a':7,'b':10, 'c':9}]      10   

如果您需要保留所有原始行，请在下面使用

In case if you need to preserve all original rows - use below

#standardSQL
CREATE TEMP FUNCTION json2array(json STRING)
RETURNS ARRAY<STRING>
LANGUAGE js AS """
  return JSON.parse(json).map(x=>JSON.stringify(x));
"""; 
WITH `project.dataset.table` AS (
  SELECT "[{'a':1,'b':4, 'c':5}, {'a':0,'b':7, 'c':8},{'a':4,'b':9, 'c':12}]" json UNION ALL
  SELECT "[{'a':9,'b':10, 'c':9}]" UNION ALL
  SELECT "[{ 'a':5,'b':10, 'c':9}, {'a':1,'b':10, 'c':9}, {'a':7,'b':10, 'c':9}]"
)
SELECT json, 
  (SELECT JSON_EXTRACT_SCALAR(x, '$.b')
  FROM UNNEST(json2array(JSON_EXTRACT(json, '$'))) x
  WHERE JSON_EXTRACT_SCALAR(x, '$.a') = '1'
  ) AS b
FROM `project.dataset.table`   

有结果

Row json                                                                        b    
1   [{'a':1,'b':4, 'c':5}, {'a':0,'b':7, 'c':8},{'a':4,'b':9, 'c':12}]          4    
2   [{'a':9,'b':10, 'c':9}]                                                     null     
3   [{ 'a':5,'b':10, 'c':9}, {'a':1,'b':10, 'c':9}, {'a':7,'b':10, 'c':9}]      10  

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