sql 2008中标识列循环自增的实现

use master;
go

if exists(select * from sys.databases where name='stuDB')
 drop database stuDB;
go

exec sp_configure 'show advanced options',1   --显示高级选项
go
reconfigure
go
exec sp_configure 'xp_cmdshell',1
go
reconfigure
go
exec xp_cmdshell 'mkdir D:\stuDB'
go

create database stuDB
on(
 name='stuDB_data',
 filename='D:\stuDB\stuDB.mdf',
 size=5MB,
 filegrowth=15%
)log on(
 name='stuDB_log',
 filename='D:\stuDB\stuDB.log'
)
go

use stuDB;
go

if exists(select * from sys.objects where name='stuInfo')
 drop table stuInfo;
go

create table stuinfo(
 stuName varchar(40) not null,
 stuNo varchar(10) primary key 
  constraint CK_stuNo check(stuNo like 'S253__'),
 stuSex varchar(2) not null default '男'
  constraint CK_stuSex check(stuSex in('男','女')),
 stuAge int
  constraint CK_stuAge check(stuAge between 15 and 30),
 stuSeat int identity(1,1),   --要求座位号只能在1-30之间，超过30从1开始重新自增
 stuAddress text default '地址不详'
);
go

--获取表中刚刚生成的自增量
select distinct(@@IDENTITY) from 表名;

--创建一个触发器，当座位号大于30则重置标识列
if exists(select * from sys.triggers where name='tr_stuinfo')
 drop trigger tr_stuinfo;
go

create trigger tr_stuinfo on stuinfo
after insert
as 
 if (select ident_current('stuinfo'))>=30
  begin
   dbcc checkident(stuinfo,reseed,0);
  end
go

 

if exists(select * from sys.objects where name='stuMarks')
 drop table stuMarks;
go

create table stuMarks(
 examNo varchar(20) not null
  constraint CK_examNo check(examNo like 'E200507____'),
 stuNo varchar(10) not null
  constraint FK_sNo foreign key references stuInfo(stuNo),
 writtenExam Numeric(5,2) default 0
  constraint CK_we check(writtenExam between 0 and 100),
 labExam Numeric(5,2) default 0
  constraint CK_le check(labExam between 0 and 100)
);