可以同时打开两个查询分析器窗体模拟多个事务并发运行
练习1——未提交读 连接1 use students go
连接2 use students go
select * from stu where name='黎明' set transaction isolation level read uncommitted go
连接1 begin tran update stu set name='黎明' go
连接2 select * from stu where name='黎明'
连接1 rollback tran go
连接2 select * from stu where name='黎明'
练习2——提交读 连接1 use students go
连接2 use students go
select * from stu where name='黎明' set transaction isolation level read committed go
连接1 begin tran update stu set name='黎明' go
连接2 select * from stu where name='黎明'
连接1 rollback tran go
连接2 select * from stu where name='黎明'
练习3——有问题的提交读（两次读取的东西不一样）和可重复读 连接1 use students go
连接2 use students go update stu set name='JIM' set transaction isolation level read committed go
begin tran select * from stu where name='黎明' go
连接1 update stu set name='黎明' go
连接2 select * from stu where name='黎明' go commit tran go
－－－－－－－－－－可重复读－－－－－－－－－－－ 连接2 set transaction isolation level repeatable read go
begin tran select * from stu where name='黎明' go
连接1 update stu set name='JIM' go
连接2 select * from stu where name='黎明' go
连接2 commit tran go select * from stu where name='黎明' select * from stu where name='JIM'
练习4——有问题的可重复读和可串行化 连接1 use students go
连接2 use students go set transaction isolation level repeatable read go begin tran select * from stu where name like '李%' go
连接1 insert stu values('000111','李树青',1,'1999-9-9',1.76)
连接2 select * from stu where name like '李%' go
－－－－－－－－－－串行化－－－－－－－－－－－（将新的插入记录删除） 连接2 commit tran set transaction isolation level serializable go
begin tran select * from stu where name like '李%' go
连接1 insert stu values('000111','李树青',1,'1999-9-9',1.76)
连接2 select * from stu where name like '李%' go
连接2 commit tran go
连接2 select * from stu where name like '李%' go