帮看下存储过程什么意思

Question

Create procedure CancelCourse
(
 @StudentID int,
 @CourseID int,
 @ElectiveID int output 
)
as
select 
@ElectiveID=ElectiveID
from
Elective
where
@StudentID=StudentID
and
@CourseID=CourseID
delete from
Elective
where
(
 @StudentID=StudentID
and
 @CourseID=CourseID
)
GO
尽量解释清楚点 我刚学的

Answer 1

Create procedure CancelCourse
--创建存储过程名称为CancelCourse
(
 @StudentID int,
 @CourseID int,
 @ElectiveID int output 
--定义三个变量，其中两了是输入的，一个是输出的
)
as
--存储过程代码
select 
@ElectiveID=ElectiveID
from
Elective
where
@StudentID=StudentID
and
@CourseID=CourseID
delete from
Elective
where
(
 @StudentID=StudentID
and
 @CourseID=CourseID
)
GO--执行

Answer 2

通过@ElectiveID返回Elective表中，被删除的CourseID=@CourseID，StudentID=@StudentID的记录的ElectiveID值

Answer 3

应楼主要求结合gaojier1000(高捷)的讲解
我补充一下
该过程就是选修课退选过程
 select 
@ElectiveID=ElectiveID
from
Elective
where
@StudentID=StudentID
and
@CourseID=CourseID
以上是从Elective表中找出符合输入的StudentID和CourseID的条目然后将相应条目的Elective字段值赋予@ElectiveIDdelete from
Elective
where
(
 @StudentID=StudentID
and
 @CourseID=CourseID
)
从Elective表中删除对应StudentID和CourseID的记录
选修课就被取消了