如何在PostgreSQL中创建命名窗口分区（别名）？ [英] How do I create named window partitions (aliases) in PostgreSQL?

问题描述

PostgreSQL窗口函数似乎暗示您可以在查询的多个位置使用相同的命名窗口。但是，我不知道如何创建命名窗口？

The documentation for PostgreSQL window functions seems to imply you can use the same named window in multiple places in your query. However, I can't figure out how do I create a named window?

SELECT first_value(vin) OVER( PARTITION BY vin ) AS w, first_value(make) OVER w
FROM inventory.vehicles
WHERE lot_Id = 9999 AND make is not null;

这是一个玩笑的查询，我正在尝试采用语法，但我得到了错误：

This is a joke query I'm trying to get the syntax to take, but I'm getting error:

错误：窗口 w不存在

ERROR: window "w" does not exist

推荐答案

答案实际上是在 SELECT doc：

The answer was actually in the SELECT doc:

WINDOW 条款

WINDOW Clause

可选的 WINDOW 子句的格式为

The optional WINDOW clause has the general form

WINDOW window_name AS（window_definition）[，...]

这里是一个例子，

SELECT first_value(vin) OVER w,
  first_value(make) OVER w
FROM inventory.vehicles
WHERE lot_Id = 9999
  AND make is not null
WINDOW w AS ( PARTITION by vin );

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