如何在内部联接中选择第二个最小值？

Question

我有这个问题

select c.id, c.name, c.email, c.totalpets, min(p.date_created) as first_order,
min(p.weight) as min_weight_bought,
max(p.weight) as max_weight_bought,
count(p.ordernumber) as total_orders
from orders p
inner join customers c
on p.customer_id = c.id
where p.approved = 1
and c.totalpets >= 1
group by c.id
having total_orders > 1

请注意，first_order 给了我该行的第一个结果，对吗？我正在尝试获得客户第一订单和客户第二订单。我怎样才能在这个内部连接中做到这一点？

谢谢

Answer 1

SELECT c1.id,
       c1.name,
       c1.email,
       c1.totalpets,
       p1.date_created
FROM orders p1
INNER JOIN customers c1
    ON p1.customer_id = c1.id
WHERE 
(
    SELECT COUNT(*)
    FROM orders p2
    INNER JOIN customers c2
        ON p2.customer_id = c2.id
    WHERE c2.id = c1.id AND p2.date_created <= p1.date_created
) <= 2 
ORDER BY c1.id;

这是一个正在运行的演示，它显示了上述查询（和简化的数据集）的简化版本：

SQLFiddle