SQL Inner用订单加入客户 [英] SQL Inner Join customers with orders

问题描述

如果我有两张桌子（其中一个客户，其信息包括地址，姓名，电子邮件等）和另一个订单（订单号，发货日期，订购该商品的客户名称），我如何显示有少于3个订单的客户的电子邮件？

我知道我必须使用内部连接和一些别名，但我不知道如何继续。 / b>

谢谢！

到目前为止：

 选择customer.email 
从customer作为cust 
 INNER JOIN（选择customer_id，sum（line_qty）AS从订单中总计
 ON ON cust。 customer_id = o.customer_id 
 where total =（SELECT total <3 
 FROM（select customer_id，sum（line_qty）AS total 
 from order as o cust.customer_id = o.customer_id 
）as sub）; 
  

解决方案

这：

  SELECT c.email 
 FROM customer AS c 
 LEFT OUTER JOIN命令AS o ON c .customer_id = o.customer_id 
 GROUP BY c.email 
 HAVING SUM（o.line_qty）< 3 
  

if I have a two tables (one of customers, with their information including address, name, emails etc) and another of orders (with order number, shipping date, customer name who ordered that item), how could I show the email of the customers who have less than 3 orders?

I know I have to use an inner join and some alias's, but i'm not sure how to proceed.

Thanks!

what I have so far:

SELECT customer.email 
FROM customer as cust 
INNER JOIN (select customer_id, sum(line_qty) AS total 
            from orders as o ON cust.customer_id = o.customer_id 
            where total = (SELECT total < 3 
                           FROM (select customer_id, sum(line_qty) AS total 
                                 from orders as o ON cust.customer_id = o.customer_id
                                ) as sub);

解决方案

Try this:

SELECT c.email 
FROM customer AS c 
LEFT OUTER JOIN orders AS o ON c.customer_id = o.customer_id 
GROUP BY c.email 
HAVING SUM(o.line_qty) < 3

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