从SQL查询中获取最大日期

问题描述

我是使用sql的初学者，我想知道是否有人可以提供帮助。 我有2张桌子 表1是如下的客户表

> POST http://localhost:8080/api/persons
> WebTestClient-Request-Id: [1]
> Content-Type: [application/json]
> Content-Length: [98]

{
  "first_name" : "John","last_name" : "Smith","age" : 25,"calculationSeed" : 0.0
}

< 201 CREATED Created
< Content-Type: [application/json]
< transfer-encoding: [chunked]
< Date: [Mon,19 Oct 2020 15:26:01 GMT]

{"first_name":"John","last_name":"Smith","age":25,"calculation_seed":0.09482345680132348}

表2是一个价值细分

CUSTOMER ID - CUSTOMER JOIN DATE
1234               01/03/2018
2345               21/07/2019

我需要做的是加入“客户”表，并带回“客户ID”和“加入日期”，然后从“价值段”表中取回具有最新“加载日期”的值，这样我的表将如下所示：

CUSTOMER ID - VALUE - LOADED_DATE
1234          HIGH     01/09/20
1234          MEDIUM   01/10/20
2345          LOW      01/09/20
2345          LOW      01/10/20

预先感谢

谢谢， 迈克

解决方法

一个选项可能正在使用row_number()

select * from
(
select cusomer_id,customer_join_date,value,row_number() over(partition by customer_id order by LOADED_DATE desc) as rn
from 
customer c inner join value_segment v on c.customer_id=v.customer_id
)A where rn=1

,

具有FIRST_VALUE()窗口功能：

select distinct c.*,first_value(v.value) over (partition by c.customerid order by v.loaded_date desc) value
from customer c inner join valuesegment v
on v.customerid = c.customerid