如何在 Google BigQuery 中的数组中的元素上创建表连接

Posted 2023-03-24

【中文标题】如何在 Google BigQuery 中的数组中的元素上创建表连接

【英文标题】：how to create a table join on elements in an Array in Google BigQuery

【发布时间】：2020-08-22 13:51:20

【问题描述】：

我有一些数据，contact_ID，它们位于一个名为 Deals 的表内的结构数组中，如下例所示。

WITH deals AS (
  Select "012345" as deal_ID,
    [STRUCT(["abc"] as company_ID, [123,678,810] as contact_ID)]
      AS associations)
SELECT 
  deal_ID,
  ARRAY(
    SELECT AS STRUCT  
      ( SELECT STRING_AGG(CAST(id AS STRING), ', ') 
        FROM t.contact_ID id
      ) AS contact_ID 
    FROM d.associations t
  ) AS contacts
FROM deals d

上面的查询获取关联数组中的contact_ID，并用逗号分隔。

Row    deal_ID    contacts.contact_ID   
1      012345     123, 678, 810

但我现在的问题是我需要将contact_IDs替换为另一个名为contacts的表中的名字和姓氏，如下所示，其中contact_ID是INT64，名称字段是字符串。

contact_id    first_name   last_name
123           Jane         Doe
678           John         Smith
810           Alice        Acre

我尝试过使用这样的子查询：

WITH deals AS (
  Select "012345" as deal_ID,
    [STRUCT(["abc"] as company_ID, [123,678,810] as contact_ID)]
      AS associations)
SELECT 
  deal_ID,
  ARRAY(
    SELECT AS STRUCT 
      company_ID, 
      ( SELECT STRING_AGG(
        (select concat(c.first_name, " ", c.last_name)
         from contacts c
         where c.contact_id=id), ', ') 
        FROM t.contact_ID id
      ) AS contact_name 
    FROM d.associations t
  ) AS contacts
FROM deals d

但这会产生错误“不支持引用其他表的相关子查询，除非它们可以去相关，例如通过将它们转换为有效的 JOIN。”但是当我需要加入的东西在 deals.associations 数组中时，我不知道如何在 deal.associations.contact_ID 和 contacts.contact_id 之间建立连接...... 提前感谢您的任何指导。

【参考方案1】：

以下是 BigQuery 标准 SQL

#standardSQL
SELECT deal_ID, 
  ARRAY_AGG(STRUCT(company_ID, contact_name)) AS contacts
FROM (
  SELECT 
    deal_ID, 
    ANY_VALUE(company_ID) AS company_ID, 
    STRING_AGG(FORMAT('%s %s', IFNULL(first_name, ''), IFNULL(last_name, '')), ', ') AS contact_name
  FROM deals d, 
    d.associations AS contact, 
    contact.contact_ID AS contact_ID
  LEFT JOIN contacts c
  USING(contact_ID)
  GROUP BY deal_ID, FORMAT('%t', company_ID)
)
GROUP BY deal_ID   

如果应用于您问题的样本数据 - 输出是

Row deal_ID     contacts.company_ID     contacts.contact_name    
1   012345      abc                     Jane Doe, John Smith, Alice Acre    

注意 - 下面

  FROM deals d, 
    d.associations AS contact, 
    contact.contact_ID AS contact_ID   

是一个快捷方式

  FROM deals, 
    UNNEST(associations) AS contact, 
    UNNEST(contact_ID) AS contact_ID

不知何故 - 这是我的偏好，尽可能不在查询文本中使用显式 UNNEST()