Postgresql 按多列分组并在每个组内排序

Question

我有一个 table 包含以下列：

order_id	amount	rating	percent	customer_id	ref_id	doc_id
1	1000	1	0.6	112	8	5
2	2000	2	0.1	111	8	8
2	3000	3	0.2	110	8	6
3	4000	5	0.1	100	7	7
3	4000	2	0.7	124	7	9
3	5000	4	0.6	143	5	10
4	2000	6	0.4	125	4	11
4	2500	1	0.55	185	4	12
4	1000	4	0.42	168	5	13
4	1200	8	0.8	118	1	14

对于每个 order_id 我想找到 doc_id 具有最高数量、最高评级、最高百分比、最低 customer_id。

对于单个订单 ID，我可以这样做：

select order_id, doc_id
from orders
where order_id = 1625
order by amount desc nulls last,
         rating desc nulls last, 
         percent desc nulls last,
         customer_id asc
limit 1;

但我没能完成所有订单。所以输出应该是这样的：

order_id	doc_id
1	5
2	6
3	10
4	12

我正在使用 Postgresql。知道我应该怎么做吗？

Answer 1

您似乎需要在 window 中实现行编号，按您想要的标准排序：

with t as (
select *,
    Row_Number() 
      over(partition by order_id 
        order by amount desc, rating desc, percent desc, customer_id
      ) seq
    from Yourtable
)
select order_id, doc_id
from t
where seq=1

Answer 2

使用FIRST_VALUE()window函数：

SELECT DISTINCT order_id, 
       FIRST_VALUE(doc_id) OVER (
         PARTITION BY order_id 
         ORDER BY amount DESC NULLS LAST, rating DESC NULLS LAST, percent DESC NULLS LAST, customer_id
       ) doc_id
FROM orders;

参见demo。

Postgresql 按多列分组并在每个组内排序

Postgresql group by multiple columns and sort within each group

sql

postgresql

sql-order-by

distinct

window-functions