已訂購最多常見產品的夫婦 - SQL

Question

我無法選擇已訂購最多常見產品的幾位客戶。

實施例：

• customer1表訂購的產品：A，B，C，Z
• 顧客2訂購產品：A，C，d，克
• customer1表訂購的產品：G，H，Z

預期結果：Customer1 | Customer2 | 2（普通產品的數量排序）

我試了一下：

SELECT c.pid, c.cid, d.cid, count(c.pid) 
FROM orders c JOIN orders d join 
(SELECT a.cid, b.cid FROM customers a JOIN customers b ON b.cname != a.cname AND b.cname > a.cname) as subq 
ON c.cid = a.cid and d.cid = b.cid 
AND c.pid = d.pid group by c.pid; 

這將返回每對夫妻的名字：

select a.cname client_1, b.cname client_2 
from customers a join customers b on b.cname != a.cname and b.cname > a.cname; 

我怎樣才能得到共同的PID的最大的一對夫婦的cids？

表：

customers (cid, cname, residence) 
orders (pid, cid, odate, quantity) 
products (pid, pname, price, origin) 

Answer 1

可能無法在每一個RDBMS工作。你在使用哪一個？

select o1.cid, o2.cid, o1.pid, o1.cnt, o2.cnt 
from (
select cid, pid, count(*) as cnt 
, ROW_NUMBER() OVER(PARTITION BY cid, pid ORDER BY count(*) DESC) AS rn 
from order 
group by cid, pid 
) as o1 
join (
select cid, pid, count(*) as cnt 
, ROW_NUMBER() OVER(PARTITION BY cid, pid ORDER BY count(*) DESC) AS rn 
from order 
group by cid, pid 
) as o2 
on o1.cid <> o2.cid 
and o1.pid = o2.pid 

where o1.rn = 1 
and o2.rn = 1