在其中选择差异的对象

Question

我试图找到一种方法来运行它：

SELECT 
    s.system_number,
    s.total_points,
    p.licensed_points,
    SUM(p.licensed_points) - SUM(s.total_points) AS difference_points
FROM 
    server AS s 
    LEFT JOIN 
        practice AS p ON p.system_number = s.system_number 
WHERE 
    difference_points < 0

我的目标是仅选择差异点<0的对象

有人知道该怎么做吗？

谢谢

Answer 1

• 在不使用Sum()的情况下使用聚合函数Group By毫无意义。您将需要在Group By上进行s.system_number。
• 然后，您可以使用Having子句来考虑difference_points小于0的情况。

请尝试以下操作：

SELECT 
    s.system_number,
    SUM(s.total_points),
    SUM(p.licensed_points),
    SUM(p.licensed_points) - SUM(s.total_points) AS difference_points
FROM 
    server AS s 
    LEFT JOIN 
        practice AS p ON p.system_number = s.system_number 
GROUP BY 
  s.system_number 
HAVING 
    difference_points < 0