摘要:
on delete cascade:外键指向记录被删除时级联删除受影响记录。alter table empadd constraint fk_emp_dept foreign key(dept) references dept(deptno) on delete cascade; 删除dept的记录时级联删除emp数据。on delete set null:外键指向记录被删除时设置受影响记录外键字段为空。alter table empadd constraint fk_emp_dept foreign key(dept) references dept(deptno) on delete se 阅读全文
posted @ 2011-07-25 17:35
爱上飞飞的面码
阅读(794)
评论(0)
推荐(0)

浙公网安备 33010602011771号