select一位顾客的随机订单

Question

我有 table 个客户和他们的订单。我想 select 每个客户的随机订单。

示例table

customer | orders
---------+---------
customerA| Order1
customerA| Order2
CustomerA| Order3
customerB| Order1
customerB| Order2
customerB| Order3
CustomerC| Order1
customerC| Order2

结果table

customer | orders
---------+---------
customerA| Order2
customerB| Order1
CustomerC| Order1

有办法吗？

Answer 1

您可以使用 row_number()（和 ANSI 标准函数）。但是，计算随机数因数据库而异。这是想法：

select t.*
from (select t.*,
             row_number() over (partition by customer order by random()) as seqnum
      from t
     ) t
where seqnum = 1;

一些随机数函数：

SQL 服务器：newid()
Postgres: random()
甲骨文：dbms_random.value
天睿数据：random(1, 999999999)
DB2：rand()
SAP 花：rand()

select一位顾客的随机订单

select a random order of a customer

sql

hana