标准 SQL 中的 BigQuery 连接数组

Posted 2023-03-24

【中文标题】标准 SQL 中的 BigQuery 连接数组

【英文标题】：BigQuery Join Array in standard SQL

【发布时间】：2016-08-10 08:42:14

【问题描述】：

我正在使用标准 SQL，并且我有表 Order：

"Order" table

我正在尝试将它与表 MenuItem 加入它

"MenuItem" table

在Order item_ids 数组和MenuItem __id__ 整数列上并获取MenuItem 价格数组，但我收到错误：

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。

如何避免这个错误？

查询：

WITH menu_items AS 
( 
    SELECT
        __id__,
        price
    FROM
        `potykion.MenuItem`
)
SELECT
    *, 
    ARRAY(
        SELECT 
           price
        FROM 
           UNNEST(item_ids) AS id
        JOIN 
            menu_items 
        ON 
            id = menu_items.__id__
    ) 
FROM 
    `potykion.Order`

【问题讨论】：

什么是item_details？我在 Orders 表的示例数据中没有看到它。

我猜item_details 是其中一张表中的记录。不过，请提供您的表的架构，其中包含几行示例和预期结果。 - 一般而言 - 请编辑您的问题以显示您遇到问题的代码的Minimal, Complete, and Verifiable example，然后我们可以尝试帮助解决具体问题。你也可以阅读How to Ask。

预期输出是什么？ - 仍然不清楚 - 是订单的字段加上订单中所有商品的总价吗？

我需要用价格数组替换 item_ids 数组

【参考方案1】：

试试下面（BigQuery 标准 SQL）

WITH Orders AS (
  SELECT 1 AS id, ARRAY[1,2,3] AS item_ids UNION ALL 
  SELECT 2 AS id, ARRAY[4,5] AS item_ids UNION ALL 
  SELECT 3 AS id, ARRAY[1,4,6] AS item_ids 
),
MenuItems AS (
  SELECT 1 AS __id__, 1.1 AS price UNION ALL
  SELECT 2 AS __id__, 1.2 AS price UNION ALL
  SELECT 3 AS __id__, 1.3 AS price UNION ALL
  SELECT 4 AS __id__, 1.4 AS price UNION ALL
  SELECT 5 AS __id__, 1.5 AS price UNION ALL
  SELECT 6 AS __id__, 1.6 AS price UNION ALL
  SELECT 7 AS __id__, 1.7 AS price 
)
SELECT 
  *, 
  ARRAY(
    SELECT price 
    FROM UNNEST(item_ids) AS id 
    JOIN MenuItems 
    ON __id__ = id
  ) AS prices
FROM Orders  

餐桌订单：

表格菜单项：

结果：

【讨论】：

好吧，我的数组创建表达式实际上是一样的，我想我得到了错误，因为 MenuItems 是另一个表。

希望我的“练习”能有所帮助！

【参考方案2】：

在数组创建表达式中加入连接的解决方案是正确的，但它不适用于单独的表。另一种解决方案是数组聚合：

WITH Orders AS (
  SELECT 1 AS id, ARRAY[1,2,3] AS item_ids UNION ALL 
  SELECT 2 AS id, ARRAY[4,5] AS item_ids UNION ALL 
  SELECT 3 AS id, ARRAY[1,4,6] AS item_ids 
),
MenuItems AS (
  SELECT 1 AS __id__, 1.1 AS price UNION ALL
  SELECT 2 AS __id__, 1.2 AS price UNION ALL
  SELECT 3 AS __id__, 1.3 AS price UNION ALL
  SELECT 4 AS __id__, 1.4 AS price UNION ALL
  SELECT 5 AS __id__, 1.5 AS price UNION ALL
  SELECT 6 AS __id__, 1.6 AS price UNION ALL
  SELECT 7 AS __id__, 1.7 AS price 
)
SELECT 
  id, ARRAY_AGG(price)
FROM Orders  
  JOIN MenuItems ON __id__ in UNNEST(item_ids)
  GROUP BY id