组合来自两个表的两个SUM操作

Question

我有两个SQL操作(它们分别正常工作):

SELECT SUM(Salary) AS StutorSum
FROM Stutor;
SELECT SUM(Salary) AS StudentAssistentSum
FROM StudentAssistent;

但是问题是我不能把它们组合起来。最后，我希望得到三个列:

1. 带有StutorSum的列
2. 带StudentAssistentSum的列
3. 与
之和的列

然而，我不能让这发生，我尝试了很多事情，在互联网上搜索，但没有工作。

有人能帮我吗?

问候,Joren

Answer 1

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;

Answer 2

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;