作业布置
练习：账号信息表，用户组，主机表，主机组
#用户表 create table user( id int not null unique auto_increment, username varchar(20) not null, password varchar(50) not null, primary key(username,password) ); #用户组表 create table usergroup( id int primary key auto_increment, groupname varchar(20) not null unique ); #主机表 create table host( id int primary key auto_increment, ip char(15) not null unique default '127.0.0.1' ); #业务线表 create table business( id int primary key auto_increment, business varchar(20) not null unique ); #建关系：user与usergroup create table user2usergroup( id int not null unique auto_increment, user_id int not null, group_id int not null, primary key(user_id,group_id), foreign key(user_id) references user(id), foreign key(group_id) references usergroup(id) ); #建关系：host与business create table host2business( id int not null unique auto_increment, host_id int not null, business_id int not null, primary key(host_id,business_id), foreign key(host_id) references host(id), foreign key(business_id) references business(id) ); #建关系：user与host create table user2host( id int not null unique auto_increment, user_id int not null, host_id int not null, primary key(user_id,host_id), foreign key(user_id) references user(id), foreign key(host_id) references host(id) );
练习:
# 班级表 cid caption # 学生表 sid sname gender class_id # 老师表 tid tname # 课程表 cid cname teacher_id # 成绩表 sid student_id course_id number