sql - 组合来自两个表的两个 SUM 运算

Question

我有两个 SQL 操作（分别正常工作）：

SELECT SUM(Salary) AS StutorSum
FROM Stutor;

SELECT SUM(Salary) AS StudentAssistentSum
FROM StudentAssistent;

`

但问题是我无法将它们结合起来。最终我想要三列作为结果：

1. StutorSum 列
2. StudentAssistentSum 列
3. 两者合计的列

但是我无法做到这一点，我尝试了很多东西，在互联网上搜索，但没有任何效果。

有人可以帮我吗？

问候，乔伦

Answer 1

我建议将查询放在FROM子句中并进行算术：

SELECT t.StutorSum, a.StudentAssistentSum,
       (t.StutorSum + a.StudentAssistentSum)
FROM (SELECT SUM(Salary) AS StutorSum
      FROM Stutor
     ) t CROSS JOIN
     (SELECT SUM(Salary) AS StudentAssistentSum
      FROM StudentAssistent
     ) a;

Answer 2

SELECT 
    SUM(Salary) AS StutorSum,
    (SELECT SUM(Salary) FROM StudentAssistent) AS StudentAssistentSum,
    (SELECT SUM(Salary) FROM Stutor) + (SELECT SUM(Salary) FROM StudentAssistent) As Total
FROM Stutor;