MySQL选择购买最多的客户名称

Question

图片中我有5张桌子彼此相连

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我尝试编写查询

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对于大多数购买，我应该考虑什么参数？

Answer 1

您可以通过调整select子句（删除order_id）来解决此问题。 然后，您将需要一个HAVING子句来实现该条件，以仅显示购买订单最多的客户。

Answer 2

SELECT lastname,firstname
FROM customer
INNER JOIN purchase_order
ON customer.customer_id=purchase_order.customer_id
GROUP BY customer_id 
ORDER BY COUNT(order_id) DESC LIMIT 1;

Answer 3

select lastname, firstname from customer c
inner join (
select customer_id, count(1) from purchase_order
group by 1
order by 2 desc limit 1) most 
/* the above sub-query named as 'most' fetched the customer id with the maximum 
number of orders */
on c.customer_id = most.customer_id; -- this is a simple join of customers table with the table generated from sub-query above

Answer 4

SELECT c.firstname,c.lastname
FROM customer c
JOIN purchase_order po
ON c.customer_id = po.customer_id
GROUP BY c.firstname,c.lastname
ORDER BY COUNT(po.order_id) DESC LIMIT 1;