SQL 43 个表合并为 1 个表

Question

刚刚开始探索数据分析的世界。

我有一个包含 43 个表的数据集，所有表都有相同的主键。 我如何从我拥有的 43 个表中创建 1 个表？

连接是做到这一点的唯一方法吗？ UNION ALL 用于所有表？有什么技巧可以让它变得更容易并且对新手友好：D。 我正在使用 BigQuery， 谢谢！

Select
AVG(duration)
from
 (SELECT
 day_of_week,
 duration,
 member_casual
 FROM
 (SELECT  started_at,
 ended_at,
 member_casual,
 DATETIME_DIFF (ended_at, started_at,minute) as duration,
 EXTRACT (DAYOFWEEK from started_at) as day_of_week
 FROM `cyclistic-406707.Trips_2020_to_2023.Trips_2023_10`)
 WHERE duration >= 0.1
 AND duration <=1440)
WHERE member_casual = "casual"

表格示例

Answer 1

为什么不直接使用 union 将表放在一起呢？ 您可以将其用于具有相同列数和数据类型的表：

SELECT_statement UNION SELECT_statement

或者，如果您有不同的结构，您可以合并相同的字段：

SELECT name
FROM customers_1
UNION
SELECT name
FROM customers_2;

Answer 2

您需要一个视图，例如：

CREATE VIEW cyclistic-406707.Trips_2020_to_2023.AllTrips
AS

SELECT *
FROM cyclistic-406707.Trips_2020_to_2023.Trips_2020_01

UNION ALL

SELECT *
FROM cyclistic-406707.Trips_2020_to_2023.Trips_2020_02

UNION ALL

...

UNION ALL

SELECT *
FROM cyclistic-406707.Trips_2020_to_2023.Trips_2023_12;

之后就可以直接VIEW查询了：

SELECT *
FROM cyclistic-406707.Trips_2020_to_2023.AllTrips
WHERE started_at BETWEEN ...
AND member_casual = "casual";

在添加中您可以添加列：

CREATE VIEW cyclistic-406707.Trips_2020_to_2023.AllTrips
AS

SELECT *, DATETIME_DIFF (ended_at, started_at,minute) as duration
FROM cyclistic-406707.Trips_2020_to_2023.Trips_2020_01

...