Question

我有一个 BigQuery 表，其中包含一列RECORD类型＆amp;模式重复。我必须在Tableau中查询并使用此表。在BigQuery中使用UNNEST或FLATTEN正在执行表的CROSS JOIN，这会影响性能。有没有其他方法可以在 Tableau 中使用此表而不展平它。已发布下面的表架构图像链接。

[表格式] https://i.stack.imgur.com/T4jHg.png

Answer 1

有没有其他方法可以使用......？

你不应该害怕UNNEST，因为它“做”了CROSS JOIN 诀窍在于，即使它是交叉连接，但它只是在行内的交叉连接，而是全局到表中的所有行。与此同时，总有办法做不同的事情因此，下面的示例1 - 使用UNNEST
呈现虚拟示例然后示例2 - 显示了如何在不使用UNNEST的情况下执行相同操作，而是使用SQL UDF
您没有提供有关您的案例的详细信息，因此下面的内容足以显示“其他”方式

Flattening via UNNEST

#standardSQL
WITH yourTable AS (
  SELECT 1 AS id, ARRAY<STRUCT<details INT64, flag STRING, value STRING, description STRING>>
    [(1,'y','a','xxx'),(2,'n','b','yyy'),(3,'y','c','zzz'),(4,'n','d','vvv')] AS type UNION ALL
  SELECT 2 AS id, ARRAY<STRUCT<details INT64, flag STRING, value STRING, description STRING>>
    [(11,'t','c','xxx'),(21,'n','a','yyy'),(31,'y','c','zzz'),(41,'f','d','vvv')] AS type
)
SELECT id, SUM(t.details) AS details
FROM yourTable, UNNEST(type) AS t
WHERE t.flag = 'y'
GROUP BY id

SQL UDF

#standardSQL
CREATE TEMP FUNCTION do_something (
  type  ARRAY<STRUCT<details INT64, flag STRING, value STRING, description STRING>>
)
RETURNS INT64 AS ((
  SELECT SUM(t.details) AS details
  FROM UNNEST(type) AS t
  WHERE t.flag = 'y'
));

WITH yourTable AS (
  SELECT 1 AS id, ARRAY<STRUCT<details INT64, flag STRING, value STRING, description STRING>>
    [(1,'y','a','xxx'),(2,'n','b','yyy'),(3,'y','c','zzz'),(4,'n','d','vvv')] AS type UNION ALL
  SELECT 2 AS id, ARRAY<STRUCT<details INT64, flag STRING, value STRING, description STRING>>
    [(11,'t','c','xxx'),(21,'n','a','yyy'),(31,'y','c','zzz'),(41,'f','d','vvv')] AS type
)
SELECT id, do_something(type) AS details
FROM yourTable

访问BigQuery RECORD - 在Tableau中重复

1 个答案: