Question

我试图在Oracle中编写一个查询，用于计算未下订单的客户数量。

以下是我一直在使用的代码：

SELECT
    COUNT(customer_num)
FROM 
    orders 
INNER JOIN 
    customer ON orders.order_num = customer.customer_num,
WHERE 
    order.order_num IS NULL;

这是错误消息：

ORA-00903：表名无效

显然这不起作用。请帮忙！

Answer 1

Select COUNT(customer_num) 
FROM customer LEFT JOIN orders ON customer.customer_num = orders.order_num  
WHERE orders.order_num is NULL;

那里有昏迷，不应该在那里而WHERE orders.order_num缺少一个＆＃34; s＆＃34;。你还有一张复数形式的表，另一张不是。也许它的表customers而不是customer？

我认为LEFT JOIN也可以更好地实现您想要实现的目标

编辑：看看这个SQL statement to get all customers with no orders

Answer 2

Select COUNT(customer_num) 
FROM orders 
right JOIN customer 
ON orders.order_num = customer.customer_num
where orders.order_num is NULL;

此外，您的客户是单数，您的订单是复数，这可能会使您在撰写查询时感到困惑。

COUNT个查询问题

2 个答案: