数据库之SQL编程

定义局部变量

declare @num int
途径一:set @num=5
途径二:select @num=5

set 和select赋值方式的区别

唯一区别,如果从数据库表中获取数据,只能用 select

declare @name nvarchar(32)
select @name =stuname
from student
where studentno=5

类型转换

declare @num int
set @num=123
print ‘num的值是‘+cast (@num as nvarchar(32))
print ‘num的值是‘+convert(nvarchar(32)@num)
--日期转成字符串
declare @mydate datetime
set @mydate =getdate()
print ‘当前时间为:‘+convert (nvarchar(32),@mydate,121)

使用SQL判定

--定义一个变量 保存avg
declare @avg int
--定义一个变量 保存科目编号
declare @subid int
select  subid=subjectid from subject
where subjectname=‘oop‘
select @avg=avg (studentresult)
from result
where examdate>=‘2013-08-09‘ and examdate <‘2013-08-10‘
and subjectid =@subid
print ‘平均分是:‘+convert (nvarchar(32),@avg)
--判定
if(@avg>=70)
begin
print ‘优秀‘
--打印出前几名的成绩
select top 3  studentno,studentresult
from result
where examdate>=‘2013-08-09‘ and examdate<‘2013-08-10‘
and subjectid =@subid
order by studentresult desc
end

else
begin
print‘差‘
--打印后几名成绩
select top 3 studentno,studentresult
from result
where examdate>=‘2013-08-09‘ and examdate<‘2013-08-10‘
and subjectid=@subid
order by studentresult asc
end
  

以上就是我刚刚学习完的使用SQL编程,有兴趣的可以继续关注我的下次博客!