c# - 我们如何在子查询 SQL Server 中分配局部变量

Question

我试图在子查询中为变量设置一个值，但它不起作用。

这是我的查询:

declare @val1 int
declare @val2 int

select @val1 = sum(column1) 
,(select @val2 = (select sum(column2) from table2))
,(@val1+@val2)Result
from table 1 

我想做的是为子查询设置 @val2 请帮助我我的意思是在子查询中设置而不是单独的选择语句

Answer 1

只需使用 3 个单独的选择:

select @val1 = sum(column1) from table1 
select @val2 = sum(column2) from table2
select (@val1+@val2) as Result

或者你也可以写2个选择:

 select @val1 = sum(column1), 
        @val2 = (select SUM(column2) from table2)
 from table1
 select (@val1 + @val2) Result

但不仅仅是 1 个选择:

A SELECT statement that assigns a value to a variable must not be combined with data-retrieval operations

如果你需要一次完成所有的选择并返回一个记录集，不要使用变量，这样做:

SELECT sum1 + sum2 FROM (
    select sum(column1) as sum1, 
           (select SUM(column2) from table2) as sum2
    from table1
) subquery