Sql 如何选择销售为0的客户（订单明细表中无记录）

如果包含的所有客户都有销售记录，如果该客户没有订单详细信息记录，则该客户甚至不会出现在以下查询中返回的行集中，则此查询已起作用。发生这种情况时，我如何补足零？ 谢谢

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似乎您只需要使用左连接

在这段代码中：

select c.CustomerCode, sum(od.NetSales) AS Sales from customer c
INNER JOIN orders o ON (c.CustomerCode = o.CustomerCode)    
INNER JOIN order_details od ON (o.OrderCode = od.OrderCode)

尝试使用：

select c.CustomerCode, sum(od.NetSales) AS Sales from customer c
LEFT JOIN orders o ON (c.CustomerCode = o.CustomerCode)    
INNER JOIN order_details od ON (o.OrderCode = od.OrderCode)

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选择c.CustomerCode，NULLIFsumNULLIFod.NetSales，0,0作为来自客户的销售c LEFT JOIN orders o ON c.CustomerCode=o.CustomerCode LEFT JOIN order_详细信息o.OrderCode=od.OrderCode group by c.CustomerCode我无法从nullifod中获得零请详细解释您想要获得的信息。

select c.CustomerCode, sum(od.NetSales) AS Sales from customer c
LEFT JOIN orders o ON (c.CustomerCode = o.CustomerCode)    
INNER JOIN order_details od ON (o.OrderCode = od.OrderCode)