如果查询返回多行，则使用TOP 1。

SELECT TOP 1 @ModelID = m.modelid 
  FROM MODELS m
 WHERE m.areaid = 'South Coast'

我更喜欢从declare语句中设置它

DECLARE @ModelID uniqueidentifer = (SELECT modelid 
                                    FROM models
                                    WHERE areaid = 'South Coast')

如果查询返回多行，则使用TOP 1。

SELECT TOP 1 @ModelID = m.modelid 
  FROM MODELS m
 WHERE m.areaid = 'South Coast'

要使用SQL选择分配变量，最佳实践如下所示

->DECLARE co_id INT ;
->DECLARE sname VARCHAR(10) ;

->SELECT course_id INTO co_id FROM course_details ;
->SELECT student_name INTO sname FROM course_details;

如果你必须在单行中分配多个变量，你可以使用同样的SELECT INTO

->DECLARE val1 int;
->DECLARE val2 int;

->SELECT student__id,student_name INTO val1,val2 FROM student_details;

--HAPPY CODING-- 

declare @ModelID uniqueidentifer

--make sure to use brackets
set @ModelID = (select modelid from models
where areaid = 'South Coast')

select @ModelID

您可以使用这个，但请记住，您的查询只给出一个结果，多个结果将抛出异常。

declare @ModelID uniqueidentifer
Set @ModelID = (select Top(1) modelid from models where areaid = 'South Coast')

另一种方法:

Select Top(1)@ModelID = modelid from models where areaid = 'South Coast'