mysql - 执行此 SQL 查询的更简洁方法

Question

所以有一个客户列表，有一个客户列表。

我有 2 个表，customers 和 invoices。

Customer_id 可以与我的客户相同，例如

客户A

Customer #1

客户端B

Customer #1

因此对于不同的客户，发票表的 customer_id 可以为 1。

下面的查询有效，但看起来有点困惑。有什么清理它的想法吗？

  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 那么 B = 1438 你不需要检查它......
(相信我，我在高中时的数学成绩为 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;

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或者明确说明您想要哪种类型的 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;