--该 read committed 默认事务隔离级别 在 systemuser修改事务未完成时   select * from  [SystemUser]  where id=62; 该语句是不可读取的

set transaction  isolation level   read committed;

begin transaction   

update [SystemUser] set LoginId='test' where id=62;

 waitfor delay '00:00:10'

commit transaction;

go

--可新建查询窗口

begin transaction   readtran

 select * from  [SystemUser]  where id=62;

commit transaction;

二、 需手动设置  读提交快照处理打开状态 设置为true —— 右键数据——选项——读提交快照处理打开状态

在 allow_snapshot_isolation on    和 set transaction  isolation level   snapshot ;模式下事务未执行完是可以读取数据的

  -- 开启快照隔离

  --alter database [SimpleFactoring15] set allow_snapshot_isolation on

  -- 关闭快照隔离

 --alter database [SimpleFactoring15] set allow_snapshot_isolation off

  -- 开启快照隔离

 alter database [SimpleFactoring15] set allow_snapshot_isolation on

 set transaction  isolation level   snapshot ;

begin transaction   

update [SystemUser] set LoginId='开启快照隔离' where id=62;

 waitfor delay '00:00:10'

commit transaction;

go

--可新建查询窗口

begin transaction   readtran

 select * from  [SystemUser]  where id=62;

commit transaction;