T-SQL 局部变量和全局变量

Posted 2021-01-23 雯烈

局部变量

 1 use StudentManageDB
 2 go
 3 --声明学号变量
 4 declare @stuid int,@stuname varchar(20)
 5 
 6 --查询李铭的信息
 7 set @stuname=‘李铭‘
 8 select StudentId,StudentName,Gender,StudentIdNo from Students
 9 where StudentName=@stuname
10 
11 --查询李铭的学号
12 select @stuId=StudentId from Students where StudentName=@stuname
13 
14 --查询与李铭学号相邻的学员
15 select StudentId,StudentName,Gender,StudentIdNo from Students
16 where StudentId=(@stuId+1) or StudentId=(@stuId-1)

set与select比较

1     declare @stuAddress nvarchar(100) , @stuName nvarchar(100)
2     --set @stuAddress=‘天津‘, @stuName=‘张三‘                            --不允许这样赋值
3     select @stuaddress=‘天津‘, @stuName=‘王小虎‘             --允许
4 
5     --set @stuAddress = (select StudentAddress from Students)  --不允许
6     select @stuAddress = StudentAddress from Students    --得到最后一个
7     set @stuAddress = (select StudentAddress from Students where 1<0) --NULL值
8     select @stuAddress =  StudentAddress from Students where 1<0        --保持原值

全局变量

1 PRINT  ‘服务器的名称: ‘ + @@SERVERNAME  
2 PRINT ‘SQL Server的版本‘ + @@VERSION 
3   
4 SELECT  @@SERVERNAME  AS  ‘服务器名称‘
5 SELECT  @@VERSION  AS  ‘SQL Server的版本‘ 

 1 use StudentManageDB
 2 go
 3 --插入学员信息
 4 insert into Students (StudentName,Gender,Age,Birthday,StudentIdNo,
 5 PhoneNumber,StudentAddress,ClassId)
 6 values(‘王小欣‘,‘男‘,28,‘1988-08-07‘,120223198808071111,
 7 ‘022-22222222‘,‘天津市南开区‘,10)
 8 
 9 
10 --获取最后一条SQL语句的执行错误号
11 print @@error