T-SQL 局部變量和全局變量

局部變量

use StudentManageDB
go
--聲明學號變量
declare @stuid int,@stuname varchar(20)

--查詢李銘的信息
set @stuname='李銘'
select StudentId,StudentName,Gender,StudentIdNo from Students
where StudentName=@stuname

--查詢李銘的學號
select @stuId=StudentId from Students where StudentName=@stuname

--查詢與李銘學號相鄰的學員
select StudentId,StudentName,Gender,StudentIdNo from Students
where StudentId=(@stuId+1) or StudentId=(@stuId-1)

set與select比較

 

    declare @stuAddress nvarchar(100) , @stuName nvarchar(100)
    --set @stuAddress='天津', @stuName='張三'                            --不允許這樣賦值
    select @stuaddress='天津', @stuName='王小虎'             --允許

    --set @stuAddress = (select StudentAddress from Students)  --不允許
    select @stuAddress = StudentAddress from Students    --得到最后一個
    set @stuAddress = (select StudentAddress from Students where 1<0) --NULL值
    select @stuAddress =  StudentAddress from Students where 1<0        --保持原值

全局變量

 

PRINT  '服務器的名稱: ' + @@SERVERNAME  
PRINT 'SQL Server的版本' + @@VERSION 
  
SELECT  @@SERVERNAME  AS  '服務器名稱'
SELECT  @@VERSION  AS  'SQL Server的版本' 

use StudentManageDB
go
--插入學員信息
insert into Students (StudentName,Gender,Age,Birthday,StudentIdNo,
PhoneNumber,StudentAddress,ClassId)
values('王小欣','男',28,'1988-08-07',120223198808071111,
'022-22222222','天津市南開區',10)


--獲取最后一條SQL語句的執行錯誤號
print @@error