摘要：
创建用户create user user_name identified by password;用户权限describe user_user_privs;查询用户(仅名字)select USERNAME from dba_users;授权会话grant create session to user 阅读全文
摘要：
create table a(aid char(2) primary key,name char(10)); create table b(bid char(2) primary key,name char(10),aid char(2)); alter table badd constraint 阅读全文