導讀:1建站知識最近需要用的oracle，所以大家好好的學習下基礎并整理下資料，希望能幫助到需要的朋友。網站建設制作網站建設哪家好。

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;seo網站優化軟件 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去掉共同網站建設制作擁有的數據 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; t網站seo優化培訓o_ymininterval()

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