--清空所有数据
--反之不行
delete from t3
go 
delete from t2
go 
delete from t1

select t2.ID,t3.ID from t1,t2,t3 where t1.name='collage'

------解决方案--------------------
先删除从表数据
再删除主表数据

一级级删

------解决方案--------------------
sysreferences
或
sysforeignkeys

可找出外健表..
--楼主的应该这个顺序和条件删除

delete t3
from  
t  
join  
t2 on t.ID=t2.t1ID and t.Name='collage'
join
t3 on t3.ID=t2ID

delete t2
from  
t  
join  
t2 on t.ID=t2.t1ID and t.Name='collage'

delete t2
from  
t  
where
Name='collage'