BigQuery LEFT JOIN 一个表并根据条件过滤其数组元素

Posted 2023-03-25

【中文标题】BigQuery LEFT JOIN 一个表并根据条件过滤其数组元素

【英文标题】：BigQuery LEFT JOIN a table and filter its array elements based on conditions

【发布时间】：2019-12-06 13:33:22

【问题描述】：

我想将一个表连接到另一个包含数组的表，并且在连接的结果中我只想拥有通过条件的数组元素。在这种情况下，日期条件。 下面的代码 sn-p 说明了我的问题。我希望输出仅包含 ids 和 record_dates 小于 '2019-10-15'

WITH platform AS (
        SELECT 'u1' AS id, 'm1' AS platform_id, '2019-10-12' as record_date
        UNION ALL
        SELECT 'u2' AS id, 'm1' AS platform_id, '2019-10-13' as record_date
        UNION ALL
        SELECT 'u21' AS id, 'm1' AS platform_id, '2019-10-16' as record_date    
), 

platform_agg AS (
        SELECT platform_id
              , ARRAY_AGG(id) as ids
              , ARRAY_AGG(record_date) as record_dates
        FROM platform
        GROUP BY platform_id
),


orders AS(
        SELECT 'u2' AS id, 'c1' AS order_id, '2019-10-15' as order_date 
), 


orders_plus_platform AS ( 
SELECT order_id
      , orders.id 
      , orders.order_date
      , platform.platform_id 
      , CASE WHEN platform.platform_id IS NOT NULL THEN platform_agg.ids ELSE [orders.id] END AS ids
      , CASE WHEN platform.platform_id IS NOT NULL THEN platform_agg.record_dates ELSE NULL END AS record_dates
FROM orders
    LEFT JOIN platform
        ON orders.id = platform.id and platform.record_date <= orders.order_date
    LEFT JOIN platform_agg
        ON platform.platform_id = platform_agg.platform_id 
)

SELECT * FROM orders_plus_platform

以下是当前查询输出，但是，在所需输出中，u21 元素应被过滤掉，因为 record_date 在“2019-10-15”之后。

谢谢你，

【问题讨论】：

理想情况下，您应该缩小问题范围，并以简洁易读的方式呈现，以便我们能够有效地帮助您。您提出的查询有太多噪音，很可能与您的问题无关，但对我们隐藏了 - 请考虑重新审视/改进您的问题

感谢您的反馈。你是对的，特别是查询应该更简洁。我做了一些编辑，我希望这些问题现在更容易理解。谢谢！

仍有很多方法可以对您的期望进行逆向工程 - 相反 - 您能否明确显示预期结果，所以我们不是在猜测

【参考方案1】：

以下解决方案对我有用。基本上，您将两次加入平台表以获取与平台关联的所有 id，而不是加入平台的预聚合版本。这样，您可以更轻松地应用过滤器。

orders_plus_platform AS ( 
SELECT order_id
      , orders.id 
      , orders.order_date
      , platform.platform_id 
      , ARRAY_AGG(CASE WHEN platform.platform_id IS NOT NULL THEN platform2.id ELSE orders.id END) AS ids
      , ARRAY_AGG(CASE WHEN platform.platform_id IS NOT NULL THEN platform2.record_date ELSE NULL END) AS record_dates
FROM orders        
    LEFT JOIN platform
        ON orders.id = platform.id and platform.record_date <= orders.order_date
    LEFT JOIN platform platform2
       ON platform.platform_id = platform2.platform_id AND platform2.record_date <= orders.order_date 
 GROUP BY     
      order_id  
      , orders.id 
      , orders.order_date
      , platform.platform_id 
)

【参考方案2】：

您可以在WHERE 子句中使用子查询。子查询可以在未嵌套的数组上运行并返回一个布尔值 - 例如日期计数

SELECT c_id
      , c.id 
      , c.c_date
      , cxd.record_id 
      , CASE WHEN cxd.record_id IS NOT NULL THEN rd_agg.ids ELSE [c.id] END AS ids
      , CASE WHEN cxd.record_id IS NOT NULL THEN rd_agg.record_dates ELSE NULL END AS record_dates
FROM c
    LEFT JOIN record_ids cxd
        ON c.id = cxd.id and cxd.record_date <= c.c_date
    LEFT JOIN record_ids_agg rd_agg
        ON cxd.record_id = rd_agg.record_id 
  WHERE (SELECT COUNT(1)>0 FROM UNNEST(record_dates) AS r WHERE r < '2019-10-15')