oracle 11g,12c安装+配置，plsql 13安装+激活

一、查询oracle中全部用户信息

select * from dba_users;
二、只查询用户和密码

select username,password from dba_users;
三、查询当前用户信息

select * from dba_ustats;

四、查询用户能够访问的视图文本

select * from dba_varrays;

五、查看用户或角色所拥有的角色

select * from dba_role_privs;   

select * from user_role_privs;

六、查看用户或角色系统权限(直接赋值给用户或角色的系统权限)

select * from dba_sys_privs;   

select * from user_sys_privs; (查看当前用户所拥有的权限)

　　oracle 建新用户

sqlplus/ as sysdba

-- create new user
CREATE USER test IDENTIFIED BY t123;

-- grant priviledges
GRANT CONNECT, RESOURCE, DBA TO test;

--alter password
alter user test identified by t123;

--oracle对表空间 USERS 无权限
alter user 用户名 quota unlimited on users;

--删除用户
drop user 用户名 cascade;   ---cascade 级联

--授予权限
-- 分配用户 Sam 建立表，建立序列，建立存储过程和建立视图的权限
grant create table,create sequence,create view,create procedure, update
to test
 
--去除用户权限
-- 去除用户 Sam 建立视图的权限
revoke create view from test;

　　建表

CREATE TABLE order_items
  (
    order_id   NUMBER( 12, 0 )                                , -- fk
    item_id    NUMBER( 12, 0 )                                ,
    product_id NUMBER( 12, 0 ) NOT NULL                       , -- fk
    quantity   NUMBER( 8, 2 ) NOT NULL                        ,
    unit_price NUMBER( 8, 2 ) NOT NULL                        ,    
    CONSTRAINT pk_order_items 
      PRIMARY KEY( order_id, item_id ),    
    CONSTRAINT fk_order_items_products 
      FOREIGN KEY( product_id )
      REFERENCES products( product_id ) 
      ON DELETE CASCADE,    
    CONSTRAINT fk_order_items_orders 
      FOREIGN KEY( order_id )
      REFERENCES orders( order_id ) 
      ON DELETE CASCADE
  );

　　插入数据：

--------------------------------------------------------------------------------------
-- Name	       : OT (Oracle Tutorial) Sample Database
-- Link	       : http://www.oracletutorial.com/oracle-sample-database/
-- Version     : 1.0
-- Last Updated: July-28-2017
-- Copyright   : Copyright ?2017 by www.oracletutorial.com. All Rights Reserved.
-- Notice      : Use this sample database for the educational purpose only.
--               Credit the site oracletutorial.com explitly in your materials that
--               use this sample database.
--------------------------------------------------------------------------------------
-- disable FK constraints 
ALTER TABLE order_items DISABLE CONSTRAINT fk_order_items_products;
ALTER TABLE order_items DISABLE CONSTRAINT fk_order_items_orders;
--------------------------------------------------------
--  OT
--------------------------------------------------------
REM INSERTING into OT.ORDER_ITEMS
SET DEFINE OFF;
Insert into OT.ORDER_ITEMS (ORDER_ID,ITEM_ID,PRODUCT_ID,QUANTITY,UNIT_PRICE) values (70,7,32,132,469.99);
Insert into OT.ORDER_ITEMS (ORDER_ID,ITEM_ID,PRODUCT_ID,QUANTITY,UNIT_PRICE) values (73,5,192,124,519.99);

-- enable FK constraints
ALTER TABLE order_items ENABLE CONSTRAINT fk_order_items_products;
ALTER TABLE order_items ENABLE CONSTRAINT fk_order_items_orders;

　　数据update

1、标准update语法（经常使用、速度可能最慢）
-- 当更新的表示单个或者被更新的字段不须要关联表带过来，此法是最好的选择。
update  a 
set a.c2= (select b.c2from  b where a.c1=b.c1)
where exists   (select 1 from   b where a.c1=b.c1)

2、内联视图更新（关联主键字段，速度较快）
-- inline view更新法就是更新一个临时创建的视图。
-- 方案：更新一个临时创建的视图。要求B表的主键字段必须在where条件中，而且是以=号来关联被更新表。
update (select a.c2 as ac2,b.c2 as bc2 from a, b where a.c1=b.c1 and a.c3=’2011’) as M 
set ac2=bc2

3、merge更新法 （关联字段非主键时，速度较快）
merge是oracle特有的语句，语法以下：
MERGE INTO table_name alias1 --主表，即须要被修改的表
USING (table | view | sub_query) alias2 --从表，即来源表
ON (join condition) --链接条件
WHEN MATCHED THEN --在匹配的记录中进行
  UPDATE table_name SET col1 = col_val1, col2 = col2_val --更改主表信息
WHEN NOT MATCHED THEN --在不匹配的状况下，筛选从表记录插入到主表【可选】
  INSERT (column_list) VALUES (column_values);

merge into a
using b 
 on (a.c1=b.c1 and a.c3=’2011’)
   when matched then
update a.c2=b.c2

4、快速游标更新法（复杂逻辑时，效率很高）
begin
    for cur in (select a.rowid  ,b.c2 from  a, b where a.c1=b.c1 and a.c3=’2011’ )  loop
        UPDATE a  set c2=cur.c2  where rowid=cur.rowid;
    end loop;
end;

　　删表

# 删表
DROP TABLE ot.order_items; 
# 删行
delete from 表名 where 条件

　　基本操做

constraint ca_pk primary key()
constraint c2 foreign key () references b()

select a,b, row_number() over(partition by a order by b) as c from aaa group by a

select a,b,rownum as id from aaa

update AAA set B=B*0.1;
commit;

update aaa set b=rownum where a='x';
commit;

update a
set (x,y)=(select x,f from a,b where a.id=b.id)
where exists(select 1 from a,b where a.id=b.id)

merge into a
using b
on 
when matched then
 update b set 
when not matched then
	insert () values()

insert into aaa(a,b)
values( 'z', 1);
commit;

insert into aaa(a,b)
(
select a, (select avg(b) from aaa)
from aaa
where a <> 'x'
);
commit;

　　经典例题

-- 查找与001号同窗所学课程彻底相同的其余同窗的学号和姓名
select t4.sid, t4.name
from (
	select sid, count(1) c1 
	from course t 
	where c1.sid <> '001'
	group by c1.sid
) t1, (
	select sid, count(1) as c2
	from course t
	where cid in (select cid from course where sid='001')
	group by sid
) t2, (
	select count(1) c3 
	from course t
	where sid='001'
) t3, (
	select sid, name 
	from student t
) t4
where t1.sid = t2.sid and t1.c1 = t2.c2 and t1.c1 = t3.c3 and t1.sid = t4.sid

　　参考资料：

ORACLE 中的union(去重并集),union all（不去重并集）,intersect（交集）,minus（减集）