SQL 具有相同 ID 但不同值的过滤器

Question

我有一个显示如下结果的查询：

CUSTOMER_ID	rented_car	BUY_dATE	SELL_dATE
001	FERRARI	01-03-2018	NULL
002	DODGE	01-03-2013	01-02-2015
001	FERRARI	01-01-2017	02-02-2020
002	DODGE	01-03-2019	NULL
002	DODGE	01-03-2019	01-03-2020
003	RENAULT	01-03-2019	01-03-2020

查询是

SELECT c.customer_id, s.name as rented_car,s.buy_date, s.sell_date
FROM company c
LEFT JOIN "user" u ON u.customer_id = c.customer_id
LEFT JOIN "cars" s ON s.customer_id = c.customer_id

我想获取目前没有租车的所有客户的 ID。如果我在 where 子句中使用类似“where sell_date IS NOT NULL”的代码，它将显示客户 ID 01,02,03，而正确答案仅为客户 ID 03.

在此先感谢您的帮助

Answer 1

您需要一个按 CUSTOMER_ID 对结果进行分组的查询。你可以尝试这样的事情：

SELECT c.customer_id
  FROM company c
  LEFT JOIN "user" u ON u.customer_id = c.customer_id
  LEFT JOIN "cars" s ON s.customer_id = c.customer_id
 GROUP BY c.customer_id
HAVING NOT bool_or(daterange(s.buy_date, s.sell_date) @> Now() :: date)

查看dbfiddle中的测试结果。

Answer 2

您可以使用 window 函数首先确定为每个客户选择哪条记录，然后应用您的 where 子句。这是一个例子

WITH cte AS 
(
  SELECT c.customer_id, 
         s.name as rented_car,
         s.buy_date, 
         s.sell_date,
         ROW_NUMBER() OVER(partition BY c.customer_id ORDER BY s.buy_date DESC) AS rn
  FROM company c
  LEFT JOIN "user" u ON u.customer_id = c.customer_id
  LEFT JOIN "cars" s ON s.customer_id = c.customer_id
)
SELECT customer_id, 
       rented_car,
       buy_date, 
       sell_date
FROM cte
WHERE rn = 1
      AND sell_date IS NOT NULL

SQL 具有相同 ID 但不同值的过滤器

SQL Filter with same ID but different values

sql

database

postgresql

join

rdbms