Question

如何取消外键关系？

比如说表stu和tea，创建时是这样
create table tea(
t_name varchar(10) not null primary key
);
create table stu(
s_name varchar(10) not null primary key,
s_myteacher(10) not null,
constraint pk_myteacher foreign key(s_myteacher) references tea(t_name)
);
要删除s_myteacher和表tea中t_name的外键关系，SQL语句应该怎么写？
如果我在设置的时候constraint pk_myteacher这项没写，那默认的约束关系是什么呢？

Answer 1

SQLSQRVER:
alter table stu drop constraint pk_myteacher

如果我在设置的时候constraint pk_myteacher这项没写，那默认的约束关系是什么呢
------------------------
可以这样查:
select t2.name from sysforeignkeys t1,sysobjects t2
where t1.constid=t2.id and t2.xtype='F' and t2.parent_obj=object_id('stu')
and t1.fkeyid=object_id('stu') and rkeyid=object_id('tea')

Answer 2

alter table stu drop constraint pk_myteacher