--新建用户create user example identified by 123456;--删除用户drop user example;--锁定用户alter user example account lock;--解锁用户alter user example account unlock;--修改用户密码alter user example identified by 654321;--授予权限，角色grant connect to example; --角色grant resource to example;grant dba to example;grant create table to example; --新建表权限grant create view to example; --新建视图权限--撤销权限，角色revoke create view from example;revoke connect from example;--新建表空间create tablespace exmpdatafile ‘G:\aaa\HP.DBF‘size 5mautoextend on next 2mmaxsize unlimited;--创建用户并设置默认表空间create user aaa identified by 123456default tablespace bbb;--用户以创建的情况下，修改用户默认表空间alter user example default tablespace aaa;--修改表空间的配额alter user example quota 10m on aaa--新建表create table emp(  empno number,  empname varchar2(10),  empsex varchar2(3));--修改表alter table emp modify empsex varchar2(10)not null; --修改字段长度alter table emp modify empsex default ‘male‘; --修该字段默认值alter table emp drop column empsex; --删除字段alter table emp add(empsex varchar2(3));--添加字段alter table emp rename column empsex to gender;--重命名字段名rename emp to emp1; --重命名表--删除表drop table emp;--设置主键alter table empadd constraint PK_empnoprimary key(empno);--设置外键create table bm( --新建一个部门表  bmno number,  bmname varchar2(20));alter table bmadd constraint PK_bmnoprimary key(bmno);alter table emp add(bmno number); --在员工表添加一个部门编号字段alter table emp    --设置bmno为外键add constraint FK_empforeign key(bmno)references bm (bmno); --设置为外键的这个字段要是另一个表中的主键--添加检查约束alter table empadd constraint C_sexcheck(empsex in (‘male‘,‘female‘));--添加唯一约束alter table empadd constraint U_nameunique(empname);--创建序列create sequence seq_empmaxvalue 999start with 1increment by 1cache 20;--使用序列select seq_emp.nextval from dual; --下一个序列值select seq_emp.currval from dual; --当前序列值insert into empvalues(seq_emp.nextval,‘jiali‘,‘male‘,22);--删除序列drop sequence seq_emp;--添加记录insert into emp(empno,empname,empsex,bmno)values(seq_emp.nextval,‘cong‘,‘female‘,22);insert into empvalues(seq_emp.nextval,‘fei‘,‘female‘,22);--删除记录delete from empwhere empno=8;--修改记录（更新）update emp set empname=‘weiwei‘ where empno=1;