T-SQL 局部变量和全局变量

局部变量

use StudentManageDB
go
--声明学号变量
declare @stuid int,@stuname varchar(20)

--查询李铭的信息
set @stuname='李铭'
select StudentId,StudentName,Gender,StudentIdNo from Students
where StudentName=@stuname

--查询李铭的学号
select @stuId=StudentId from Students where StudentName=@stuname

--查询与李铭学号相邻的学员
select StudentId,StudentName,Gender,StudentIdNo from Students
where StudentId=(@stuId+1) or StudentId=(@stuId-1)

set与select比较

    declare @stuAddress nvarchar(100) , @stuName nvarchar(100)
    --set @stuAddress='天津', @stuName='张三'                            --不允许这样赋值
    select @stuaddress='天津', @stuName='王小虎'             --允许

    --set @stuAddress = (select StudentAddress from Students)  --不允许
    select @stuAddress = StudentAddress from Students    --得到最后一个
    set @stuAddress = (select StudentAddress from Students where 1<0) --NULL值
    select @stuAddress =  StudentAddress from Students where 1<0        --保持原值

全局变量

PRINT  '服务器的名称: ' + @@SERVERNAME  
PRINT 'SQL Server的版本' + @@VERSION 
  
SELECT  @@SERVERNAME  AS  '服务器名称'
SELECT  @@VERSION  AS  'SQL Server的版本' 

use StudentManageDB
go
--插入学员信息
insert into Students (StudentName,Gender,Age,Birthday,StudentIdNo,
PhoneNumber,StudentAddress,ClassId)
values('王小欣','男',28,'1988-08-07',120223198808071111,
'022-22222222','天津市南开区',10)


--获取最后一条SQL语句的执行错误号
print @@error