Question

有一个客户列表，其中包含客户列表。

我有2个表，customers和invoices。

Customer_id对我的客户来说可能是相同的，例如

客户A

Customer #1

客户B

Customer #1

因此，对于不同的客户，发票表的customer_id可以为1。

以下查询有效，但看起来有点凌乱。有任何清理它的想法吗？

  SELECT   name, 
           sum(sub_total) total
    FROM   customers, invoices
   WHERE   customer_id = 1438 and 
           invoices.customer_id = 1438 and 
           customers.customer_id = invoices.customer_id 
GROUP BY   name 
Order By   total DESC;

Answer 1

如果A = B和A = 1438然后B = 1438您不需要检查它...
（相信我这个，我在高中学习数字 60 + ）

SELECT   name, sum(sub_total) total    
FROM     customers, invoices    
WHERE    invoices.customer_id  = 1438
AND      customers.customer_id = invoices.customer_id 
GROUP BY name 
ORDER BY total DESC;

或者明确说明你想要哪种类型的JOIN：

SELECT   name, sum(sub_total) total    
FROM     customers  INNER JOIN invoices 
ON       customers.customer_id = invoices.customer_id 
WHERE    invoices.customer_id  = 1438
GROUP BY name 
ORDER BY total DESC;

Answer 2

你不需要额外的支票......

SELECT name, sum(sub_total) total
FROM customers, invoices
WHERE 
customer_id = 1438 and 
customers.customer_id = invoices.customer_id 
GROUP BY name order by total DESC;

Answer 3

我强烈不会在名字上做一个小组...假设你有两个名为“Bill Smith”的客户，但一个是客户ID 10，另一个是客户ID 785 ......你只是将它们组合成一个单身人士。你应该按ID分组，而不是名字......

现在，就是说，无论如何，您只查询一个客户ID，并且只会返回一条记录。如果您真正想要完成的是获取所有客户及其各自的发票，请删除单个客户的where子句。您可以按ID保留组，但显示实际客户的名称。如果您有多个客户具有相同的总数，则可以按名称进行子排序，但分组仅基于客户的ID进行分组。

SELECT
      c.name, 
      sum(i.sub_total) total
   FROM
      customers
         JOIN invoices
            on c.Customer_ID = i.Customer_ID
   GROUP BY
      c.customer_ID 
   Order By
      total DESC,
      c.Name

一种更简洁的方法来执行此SQL查询

3 个答案: