一、控制用户存取

1、创建修改用户Creating Users

Create/alter user new_user identified by password;

例：create user user_1 indentified by pwd_1

alter user user_1 identified by pwd_2

2、给用户授予权限

grant privilege[,privilege] to user [,user|role,public...]

一些系统权限：

create session/table/sequence/view/procedure

alter/delete/execute/index/insert/references/select/update

grant object_priv [(columns)]

on object

to {user|role|public}

[with grant option]

例如:

给用户user_1授予查询tt1表的权限

grant select on tt1表 to user_1

给用户user_1授予修改“表1”中(列1，列2)的权限

grant update(列1，列2) on 表1 to user_1;

给用户user_1 授予查询权限并可以把该权限授予其他用户的权限

grant select

on tt1表

to user_1

with grant option

把权限授予所有用户

grant select

on 表1

to public;

给用户user_1授权

grant create session to user_1;

二、创建角色并给角色授权

1、创建角色

create role mangager;

例如：create role test_role1;

2、给角色授权

grant create table,create view to manager;

例如：grant create table to test_role1;

3、把角色授予用户

grant manager to user_1,user_2...

grant test_user1 to user_1;

三、取消用户权限

revoke {privilege [,privilege...]|all}

on object

from {user[,user...]|role|public}

[cascade constraints];

revoke select on 表1 from user_1;

四、Database Links

create public database link hq.acme.com using 'sales';

select * from emp@hq.acme.com;

五、 oracle取并集、交集、差集

所取的列的数据类型必须兼容

1、取并集

union ：会对数据排序，重复记录压缩，union all不会

select employee_id,job_id from employess

union

select employee_id,job_id from job_history;

取所有并集不去除重复数据

select employee_id,job_id from employess

union all

select employee_id,job_id from job_history;

2、取交集

select employee_id,job_id from employess

intersect

select employee_id,job_id from job_history;

3、差集

表employess去掉共同拥有的数据

select employee_id,job_id from employess

minus

select employee_id,job_id from job_history;

六、日期时间函数

求时差

select tz_offset('US/Eastern') from dual;

alter session set time_zone='-8:0';

select sessiontimezone,current_date from dual;

alter session set time_zone='-8:0';

select sessiontimezone,current_timestamp from dual;

alter session set time_zone='-8:0';

select current_timestamp,localtimestamp from dual;

select dbtimezone,sessiontimezone from dual;

select from_tz(timestamp'2000-03-23 08:00:00','3:00') from dual;

select to_timestamp('2000-02-01 11:00:00','YYYY-MM-DD HH:MI:SS')from dual;

select to_timestamp_tz('2000-02-01 11:00:00','YYYY-MM-DD HH:MI:SS TZH:TZM')from dual;

to_ymininterval()