一、控制用戶存取
1、創建修改用戶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、給用戶授予權限
grant privilege[,privilege] to user [,user|role,public...]
一些系統權限：
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:
給用戶user_1授予查詢tt1表的權限
grant select on tt1表 to user_1
給用戶user_1授予修改“表1”中(列1，列2)的權限
grant update(列1，列2) on 表1 to user_1;
給用戶user_1 授予查詢權限并可以把該權限授予其他用戶的權限
grant select
on tt1表
to user_1
with grant option
把權限授予所有用戶
grant select
on 表1
to public;

給用戶user_1授權
grant create session to user_1;

二、創建角色并給角色授權
1、創建角色
create role mangager;
例如：create role test_role1;
2、給角色授權
grant create table,create view to manager;
例如：grant create table to test_role1;

3、把角色授予用戶
grant manager to user_1,user_2...
grant test_user1 to user_1;

三、取消用戶權限
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
所取的列的數據類型必須兼容
1、取并集
union ：會對數據排序，重復記錄壓縮，union all不會
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復數據
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去掉共同擁有的數據
select employee_id,job_id from employess
minus
select employee_id,job_id from job_history;

六、日期時間函數
求時差
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()