从 AWS Athena 或 Presto 中的 Json 中提取答案

【问题标题】：Extracting from Json in AWS Athena or Presto从 AWS Athena 或 Presto 中的 Json 中提取
【发布时间】：2020-01-21 12:53:36
【问题描述】：

我下面的查询没有给我任何结果

 WITH dataset AS (
    SELECT responseelements FROM cloudtrail_logs 
    WHERE useridentity.type = 'Root'
    AND eventname='CreateVpc'
    ORDER BY eventsource, eventname;
        AS blob
    )
    SELECT
      json_extract(blob, '$.vpc.vpcId') AS name,
      json_extract(blob, '$.ownerId') AS projects
    FROM dataset

但如果我只运行内部查询

SELECT responseelements FROM cloudtrail_logs 
WHERE useridentity.type = 'Root'
AND eventname='CreateVpc'
ORDER BY eventsource, eventname;

它给了我作为 Json 的正确响应

{"requestId":"40aaffac-2c53-419e-a678-926decc48557","vpc":{"vpcId":"vpc-01eff2919c7c1da07","state":"pending","ownerId":"347612567792","cidrBlock":"10.0.0.0/26","cidrBlockAssociationSet":{"items":[{"cidrBlock":"10.0.0.0/26","associationId":"vpc-cidr-assoc-04136293a8ac73600","cidrBlockState":{"state":"associated"}}]},"ipv6CidrBlockAssociationSet":{},"dhcpOptionsId":"dopt-92df95e9","instanceTenancy":"default","tagSet":{},"isDefault":false}}

如果我将其作为数据传递如下

WITH dataset AS (

SELECT '{"requestId":"40aaffac-2c53-419e-a678-926decc48557","vpc":{"vpcId":"vpc-01eff2919c7c1da07","state":"pending","ownerId":"347612567792","cidrBlock":"10.0.0.0/26","cidrBlockAssociationSet":{"items":[{"cidrBlock":"10.0.0.0/26","associationId":"vpc-cidr-assoc-04136293a8ac73600","cidrBlockState":{"state":"associated"}}]},"ipv6CidrBlockAssociationSet":{},"dhcpOptionsId":"dopt-92df95e9","instanceTenancy":"default","tagSet":{},"isDefault":false}}'

    AS blob
)
SELECT
  json_extract(blob, '$.vpc.vpcId') AS name,
  json_extract(blob, '$.ownerId') AS projects
FROM dataset

它给了我结果，我在这里缺少什么？这样我就可以一口气运行有可能吗？

【问题讨论】：

标签： json amazon-web-services presto amazon-athena

【解决方案1】：

您在查询中引用了错误的列名，它应该是 json_extract(responseelements, '$.vpc.vpcId') AS name 而不是 json_extract(blob, '$.vpc.vpcId') AS name。这个查询的AS blob 部分什么都不做，因为你不能为整个查询设置别名，所以把它去掉。

AS blob 在您的最后一个示例中有效，因为您正在将一个值（json 字符串）选择到一个列中，而AS blob 为该列提供了一个名称或“blob”的别名 .在您的原始查询中，您选择了一个名为 responseelements 的现有列，这就是您需要在 json_extract 函数中引用的内容。

【讨论】：