如何从 JSON 元素中提取所有值？

Question

如何提取元素account_code的所有值？ 下面的SELECT语句让我提取与索引[x]关联的任何单个值，但我想提取所有值（每个值都在它自己的行中），这样 output 是：

account_codes
------------
1
2
3

---

SELECT
    JSON_EXTRACT_SCALAR(v, '$.accounting[0].account_code') AS account_codes
FROM (VALUES JSON '
    {"accounting":
        [
            {"account_code": "1", "account_name": "Travel"},
            {"account_code": "2", "account_name": "Salary"},
            {"account_code": "3", "account_name": "Equipment"},
        ]
    }'
) AS t(v)

Answer 1

您需要使用的运算符是 unnest ，它将展平数组并获取所有列值。 下面是 hive 目录中的查询和 DDL 我用来创建表并获取所有帐户代码

DDL：

CREATE EXTERNAL TABLE `sf_73515497`(
  `accounting` array<struct<account_code:string,account_name:string>> COMMENT 'from deserializer')
ROW FORMAT SERDE 
  'org.openx.data.jsonserde.JsonSerDe' 
WITH SERDEPROPERTIES ( 
  'paths'='accounting') 
STORED AS INPUTFORMAT 
  'org.apache.hadoop.mapred.TextInputFormat' 
OUTPUTFORMAT 
  'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION
  's3://path-to-json-prefix/'

SQL 与未嵌套：

WITH dataset AS (
  SELECT accounting from "sf_73515497" 
)
SELECT t.accounts.account_code FROM dataset
CROSS JOIN UNNEST(accounting) as t(accounts)