SQL Server - Sub Query中的多个行

Question

这个查询工作单行但是，我想减去多行

SELECT(
(SELECT num1 from table1 where T_Type=2) - 
(SELECT num2 from table1 where T_Type=3))as
[SUBSTRACTION]

Answer 1

尝试

SELECT t1.num1-t2.num2 from table1 t1,table1 t2 where t1.T_Type=2 and t2.T_Type=3

Answer 2

如何根据类型对num进行求和并减去这些结果，如下所示：

SELECT (  
(SELECT SUM(num1) FROM table1 WHERE T_Type = 2) -  
(SELECT SUM(num2) FROM table1 WHERE T_Type = 3))