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