1.当数据库中的数据不小心删除或者删除之后想恢复,可以通过下面的语句查询删除之后限定时间之内的数据:

注意使用管理员登录系统:

select * from 表名 as of timestamp sysdate-1/12   //查询两个小时前的某表数据!既然两小时以前的数据都得到了,继续怎么做,知道了吧。。


如果drop了表,怎么办??见下面:

drop table 表名;


数据库误删除表之后恢复:(
绝对ok,我就做过这样的事情,汗)不过要记得删除了哪些表名。
flashback table 表名 to before drop;

2.查询得到当前数据库中锁,以及解锁:

查锁
SELECT /*+ rule */ s.username,
decode(l.type,'TM','TABLE LOCK',
'TX','ROW LOCK',
NULL) LOCK_LEVEL,
o.owner,o.object_name,o.object_type,
s.sid,s.serial#,s.terminal,s.machine,s.program,s.osuser
FROM v$session s,v$lock l,dba_objects o
WHERE l.sid = s.sid
AND l.id1 = o.object_id(+)
AND s.username is NOT NULL;

解锁
alter system kill session 'sid,serial';
如果解不了。直接倒os下kill进程kill -9 spid


ORA-28000:账户被锁定

因为密码输入错误多次用户自动被锁定.

解决办法:alter user user_name account unlock;

3.关于查询数据库用户,权限的相关语句:

1.查看所有用户:  
select * from dba_user;  
select * from all_users;  
select * from user_users;  
                                                            
                                                            
2.查看用户系统权限:  
select * from dba_sys_privs;  
select * from all_sys_privs;  
select * from user_sys_privs;  
                                                            
                                                            
3.查看用户对象权限:  
select * from dba_tab_privs;  
select * from all_tab_privs;  
select * from user_tab_privs;  
                                                            
                                                            
4.查看所有角色:  
select * from dba_roles;  
                                                            
                                                            
5.查看用户所拥有的角色:  
select * from dba_role_privs;  
select * from user_role_privs; 

4.几个经常用到的oracle视图:注意表名使用大写....................

1. 查询oracle中所有用户信息  
       select  * from dba_user;  
   2. 只查询用户和密码  
       select username,password from dba_users;  
   3. 查询当前用户信息  
       select * from dba_ustats;  
   4. 查询用户可以访问的视图文本  
       select * from dba_varrays;  
   5. 查询数据库中所有视图的文本  
       select * from dba_views;  
6.查询全部索引   
select * from user_indexes;  
查询全部表格  
      select * from user_tables;  
         查询全部约束  
      select * from user_constraints;  
          查询全部对象  
      select * from user_objects; 

5.查看当前数据库中正在执行的语句,然后可以继续做很多很多事情,例如查询执行计划等等

(1).查看相关进程在数据库中的会话     
  Select   a.sid,a.serial#,a.program,   a.status   ,     
  substr(a.machine,1,20),   a.terminal,b.spid     
  from   v$session   a,   v$process   b     
  where   a.paddr=b.addr     
  and   b.spid   =   &spid;     
                                                    
(2).查看数据库中被锁住的对象和相关会话     
  select   a.sid,a.serial#,a.username,a.program,     
  c.owner,   c.object_name       
  from   v$session   a,   v$locked_object   b,   all_objects   c     
  where   a.sid=b.session_id   and     
  c.object_id   =   b.object_id;     
                                                    
(3).查看相关会话正在执行的SQL     
  select sql_text from v$sqlarea where address = ( select sql_address   from v$session where sid = &sid );

6.查询表的结构:表名大写!!

select t.COLUMN_NAME,
      t.DATA_TYPE,
      nvl(t.DATA_PRECISION, t.DATA_LENGTH),
      nvl(T.DATA_SCALE, 0),
      c.comments
 from all_tab_columns t, user_col_comments c
whEre t.TABLE_NAME = c.table_name
  and t.COLUMN_NAME = c.column_name
  and t.TABLE_NAME = UPPER('OM_EMPLOYEE_T')
order by t.COLUMN_ID      

7.行列互换:

建立一个例子表:  
CREATE TABLE t_col_row(   
ID INT,   
c1 VARCHAR2(10),   
c2 VARCHAR2(10),   
c3 VARCHAR2(10));   
INSERT INTO t_col_row VALUES (1, 'v11', 'v21', 'v31');   
INSERT INTO t_col_row VALUES (2, 'v12', 'v22', NULL);   
INSERT INTO t_col_row VALUES (3, 'v13', NULL, 'v33');   
INSERT INTO t_col_row VALUES (4, NULL, 'v24', 'v34');   
INSERT INTO t_col_row VALUES (5, 'v15', NULL, NULL);   
INSERT INTO t_col_row VALUES (6, NULL, NULL, 'v35');   
INSERT INTO t_col_row VALUES (7, NULL, NULL, NULL);   
COMMIT;   
                                    
下面的是列转行:创建了一个视图  
CREATE view v_row_col AS 
SELECT id, 'c1' cn, c1 cv  
FROM t_col_row  
UNION ALL 
SELECT id, 'c2' cn, c2 cv  
FROM t_col_row  
UNION ALL 
SELECT id, 'c3' cn, c3 cv FROM t_col_row;  
                                    
下面是创建了没有空值的一个竖表:  
CREATE view v_row_col_notnull AS 
SELECT id, 'c1' cn, c1 cv  
 FROM t_col_row   
where c1 is not null 
UNION ALL 
SELECT id, 'c2' cn, c2 cv  
 FROM t_col_row  
where c2 is not null 
UNION ALL 
SELECT id, 'c3' cn, c3 cv  
 FROM t_col_row   
where c3 is not null; 

8.下面可能是dba经常使用的oracle视图吧

1.示例:已知hash_value:3111103299,查询sql语句:  
select * from v$sqltext   
where hashvalue='3111103299' 
order by piece   
2.查看消耗资源最多的SQL:  
SELECT hash_value, executions, buffer_gets, disk_reads, parse_calls  
FROM V$SQLAREA  
WHERE buffer_gets > 10000000OR disk_reads > 1000000  
ORDERBY buffer_gets + 100 * disk_reads DESC;  
                            
3.查看某条SQL语句的资源消耗:  
SELECT hash_value, buffer_gets, disk_reads, executions, parse_calls  
FROM V$SQLAREA  
WHERE hash_Value = 228801498AND address = hextoraw('CBD8E4B0');  
                            
4.查询sql语句的动态执行计划:  
        首先使用下面的语句找到语句的在执行计划中的address和hash_code  
        SELECT sql_text, address, hash_value FROM v$sql t  
                where (sql_text like '%FUNCTION_T(表名大写!)%')  
        然后:  
        SELECT operation, options, object_name, cost FROM v$sql_plan  
                WHERE address = 'C00000016BD6D248' AND hash_value = 664376056;  
                            
5.查询oracle的版本:  
select * from v$version;  
                            
6.查询数据库的一些参数:  
select * from v$parameter  
                            
7.查找你的session信息  
SELECT SID, OSUSER, USERNAME, MACHINE, PROCESS  
FROM V$SESSION WHERE audsid = userenv('SESSIONID');  
                            
8.当machine已知的情况下查找session  
SELECT SID, OSUSER, USERNAME, MACHINE, TERMINAL  
FROM V$SESSION  
WHERE terminal = 'pts/tl' AND machine = 'rgmdbs1';  
                            
9.查找当前被某个指定session正在运行的sql语句。假设sessionID为100  
select b.sql_text   
from v$session a,v$sqlarea b   
where a.sql_hashvalue=b.hash_value and a.sid=100

9.树形结构connect by 排序:

查询树形的数据结构,同时对一层里面的数据进行排序  
SELECT last_name, employee_id, manager_id, LEVEL 
      FROM employees  
      START WITH employee_id = 100  
      CONNECT BY PRIOR employee_id = manager_id  
     <SPAN style="BACKGROUND-COLOR: #ff0000"> ORDER SIBLINGS BY last_name;</SPAN>  
                      
                      
                      
                      
                      
                      
下面是查询结果  
LAST_NAME                 EMPLOYEE_ID MANAGER_ID      LEVEL 
------------------------- ----------- ---------- ----------  
King                              100                     1  
Cambrault                         148        100          2  
Bates                             172        148          3  
Bloom                             169        148          3  
Fox                               170        148          3  
Kumar                             173        148          3  
Ozer                              168        148          3  
Smith                             171        148          3  
De Haan                           102        100          2  
Hunold                            103        102          3  
Austin                            105        103          4  
Ernst                             104        103          4  
Lorentz                           107        103          4  
Pataballa                         106        103          4  
Errazuriz                         147        100          2  
Ande                              166        147          3  
Banda                             167        147          3  

10.有时候写多了东西,居然还忘记最基本的sql语法,下面全部写出来,基本的oracle语句都在这里可以找到了。是很基础的语句!

1.在数据字典查询约束的相关信息:  
SELECT constraint_name, constraint_type,search_condition  
FROM        user_constraints WHERE        table_name = 'EMPLOYEES';  
        //这里的表名都是大写!  
2对表结构进行说明:  
   desc Tablename  
3查看用户下面有哪些表  
   select table_name from user_tables;  
4查看约束在那个列上建立:  
   SELECT constraint_name, column_name  
   FROM        user_cons_columns  
   WHERE          table_name = 'EMPLOYEES';  
10结合变量查找相关某个表中约束的相关列名:  
  select constraint_name,column_name from user_cons_columns where table_name = '&tablename' 
12查询数据字典看中间的元素:  
SELECT   object_name, object_type  
FROM     user_objects  
WHERE    object_name LIKE 'EMP%'       
OR       object_name LIKE 'DEPT%' 
14查询对象类型:  
SELECT DISTINCT object_type FROM           user_objects ;  
17改变对象名:(表名,视图,序列)  
  rename  emp to emp_newTable  
18添加表的注释:  
  COMMENT ON TABLE employees IS 'Employee Information';  
20查看视图结构:  
   describe view_name  
23在数据字典中查看视图信息:  
  select viewe_name,text from user_views  
25查看数据字典中的序列:  
  select * from user_sequences  
33得到所有的时区名字信息:  
        select  * from v$timezone_names  
34显示对时区‘US/Eastern’的时区偏移量  
        select TZ_OFFSET('US/Eastern') from DUAL--dual英文意思是‘双重的’  
   显示当前会话时区中的当前日期和时间:  
   ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';--修改显示时间的方式的设置  
   ALTER SESSION SET TIME_ZONE = '-5:0';--修改时区  
   SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL;--真正有用的语句!  
  SELECT CURRENT_TIMESTAMP FROM DUAL;--返回的时间是当前日期和时间,含有时区  
  SELECT CURRENT_TIMESTAMP FROM DUAL;--返回的时间是当前日期和时间,不含有时区!!!    
35显示数据库时区和会话时区的值:  
        select datimezone,sessiontimezone from dual;  
                 
13普通的建表语句:  
CREATE TABLE dept  
(deptno         NUMBER(2),  
dname         VARCHAR2(14),  
loc         VARCHAR2(13));  
15使用子查询建立表:  
 CREATE TABLE         dept80  
  AS  SELECT  employee_id, last_name,   
            salary*12 ANNSAL,   
            hire_date   FROM    employees   WHERE   department_id = 80;  
6添加列:// alter table EMP add column (dept_id number(7));错误!!  
  alter table EMP add (dept_id number(7));  
7删除一列:  
  alter table emp drop column dept_id;  
8添加列名同时和约束:  
 alter table EMP add (dept_id number(7)   
   constraint my_emp_dept_id_fk  references dept(ID));  
9改变列://注意约束不能够修改 的!!  
 alter table dept80 modify(last_name varchar2(30));//这里使用的是modify而不是alter!  
24增加一行:  
  insert into table_name values();  
                 
5添加主键:  
 alter Table EMP  add constraint my_emp_id_pk primary key (ID);  
11添加一个有check约束的新列:  
  alter table EMP  
  add (COMMISSION number(2) constraint emp_commission_ck check(commission>0))  
16删除表:  
   drop table emp;  
19创建视图:  
   CREATE VIEW         empvu80  
 AS SELECT  employee_id, last_name, salary  
    FROM    employees     WHERE   department_id = 80;  
21删除视图:  
   drop view view_name  
22找到工资最高的5个人。(top-n分析)(行内视图)  
 select rownum,employee_id from (select employee_id,salary from 
 employees order by salary desc)  
  where rownum<5;  
26建立同义词:  
  create synonym 同义词名 for 原来的名字  
或者  create public synonym 同义词名 for 原来的名字  
27建立序列:(注意,这里并没有出现说是哪个表里面的序列!!)  
  CREATE SEQUENCE dept_deptid_seq  
                INCREMENT BY 10  
                START WITH 120  
                MAXVALUE 9999  
                NOCACHE  
                NOCYCLE    
28使用序列:  
        insert into dept(ID,NAME) values(DEPT_ID_SEQ.nextval,'Administration');  
29建立索引://默认就是nonunique索引,除非使用了关键字:unique 
        CREATE INDEX emp_last_name_idx ON employees(last_name);  
30建立用户:(可能有错,详细查看帮助)  
        create user  username(用户名)  
        identified by oracle(密码)  
        default tablespace  data01(表空间名//默认存在system表空间里面)  
        quota 10M(设置大小,最大为unlimited)  on 表空间名//必须分配配额!  
31创建角色:create ROLE manager  
    赋予角色权限:grant create table,create view to manage  
    赋予用户角色:grant manager to DENHAAN,KOCHHAR( 两个用户)  
32分配权限:  
        GRANT  update (department_name, location_id)  
        ON     departments  
        TO     scott, manager;  
    回收权限  
        REVOKE  select, insert 
        ON      departments  
        FROM    scott;  
36从时间中提取年,月,日:使用函数extract  
        select extract(year from sysdate) year,extract(month from sysdate),  
extract(day from sysdate) from dual;  
37使用函数得到数月之后的日期:to_yminterval(‘01-02’)表示加上1年2月,不能够到天!!  
        select hire_date,hire_date +to_yminterval('01-02') as hire_date_new from employees where department_id=20  
    得到多少天之后的日期:直接日期加数字!  
        select hire_date +3 from employees where department_id=20  
38一般的时间函数:  
        MONTHS_BETWEEN ('01-SEP-95','11-JAN-94')--两个日期之间的月数,返回一个浮点数  
        ADD_MONTHS ('11-JAN-94',6)--添加月数  
          NEXT_DAY ('01-SEP-95','FRIDAY') --下一个星期五的日期  
        LAST_DAY('01-FEB-95')--当月的最后一天!  
        ROUND(SYSDATE,'MONTH')         --四舍五入月  
        ROUND(SYSDATE ,'YEAR')       --四舍五入年  
        TRUNC(SYSDATE ,'MONTH')        --阶段月  
         TRUNC(SYSDATE ,'YEAR')        --截断年    
39 group语句:和高级的应用语句:  
        SELECT   department_id, job_id, SUM(salary),  COUNT(employee_id) FROM     employees  
                GROUP BY department_id, job_id ;  
        使用having进行约束:  
        1.group by rollup:对n列组合得到n+1种情况  
        SELECT   department_id, job_id, SUM(salary)        FROM     employees  WHERE    department_id < 60 GROUP BY ROLLUP(department_id, job_id);  
        2.group by cube:得到2的n次方种情况  
        SELECT   department_id, job_id, SUM(salary) FROM     employees  WHERE    department_id < 60 GROUP BY CUBE (department_id, job_id) ;  
        3.使用grouping得到一行中构成列的情况,只是返回1和0:是空的话就返回1,否则返回0(注意不要弄反了!)  
        SELECT   department_id DEPTID, job_id JOB,  SUM(salary),    GROUPING(department_id) GRP_DEPT,    GROUPING(job_id) GRP_JOB  
                FROM     employees WHERE    department_id < 50 GROUP BY ROLLUP(department_id, job_id);  
        4.grouping sets:根据需要得到制定的组合情况  
        SELECT   department_id, job_id, manager_id,avg(salary) FROM     employees GROUP BY GROUPING SETS ((department_id,job_id), (job_id,manager_id));  
40from中使用子查询:返回每个部门中大于改部门平均工资的与员工信息  
        SELECT  a.last_name, a.salary, a.department_id, b.salavg  FROM    employees a,--下面的地方就是子查询了,主要返回的是一组数据!  
         (SELECT   department_id, AVG(salary) salavg   FROM     employees  GROUP BY department_id) b  
        WHERE   a.department_id = b.department_id  
        AND     a.salary > b.salavg;  
41exists语句的使用:  
        SELECT employee_id, last_name, job_id, department_id  
        FROM   employees outer--下面的 exists里面的select选择出来的是随便的一个字符或者数字都可以  
        WHERE  EXISTS ( SELECT 'X'   FROM   employees WHERE  manager_id =  outer.employee_id);  
42厉害的with语句:  
        WITH   
         dept_costs  AS (--定义了一个临时的表  
                   SELECT  d.department_name, SUM(e.salary) AS dept_total--其间定义了一个临时的列dept_total  
                   FROM    employees e, departments d  
                   WHERE   e.department_id = d.department_id  
                   GROUP BY d.department_name),/*注意这里有逗号*/  
        avg_cost    AS (  
           SELECT SUM(dept_total)/COUNT(*) AS dept_avg  
           FROM   dept_costs)--这里的第二张临时表里面就引用了前面定义的临时表和之间的列!  
        SELECT *  FROM   dept_costs  WHERE  dept_total >  (SELECT dept_avg   FROM avg_cost) ORDER BY department_name;---最后的查询语句中使用了前面的临时表  
43遍历树:  
        SELECT employee_id, last_name, job_id, manager_id  
        FROM   employees  
        START  WITH  employee_id = 101  
        CONNECT BY PRIOR manager_id = employee_id ;--自底向上的遍历树。  
                 
44.更新语句  
UPDATE employees SET   
    job_id = 'SA_MAN', salary = salary + 1000, department_id = 120   
    WHERE first_name||' '||last_name = 'Douglas Grant';   
                 
UPDATE TABLE (SELECT projs   
           FROM dept d WHERE d.dno = 123)  p   
  SET p.budgets = p.budgets + 1   
  WHERE p.pno IN (123, 456);

11.导入导出dmp文件:

imp 用户名/密码@数据库 ignore=y file=备份文件 log=D:\DBtest\db_bak\imp.log


exp system/manager@TEST file=d:\daochu.dmp full=y

12.大对象字段blob:查看blob字段的大小:

  selectdbms_lob.getLength(字段名)  from表名 ;  


13.下面收集的是有意思的sql语句,说不定正是你需要的:

--创建一个只允许在工作时间访问的视图  
create or replace view newviewemp  
as  
select * from 表名  
 where exists(select 1 from dual where sysdate >=  
       to_date(to_char(sysdate, 'yyyy-mm-dd ') || '08:00:00', 'yyyy-mm-dd hh24:mi:ss')  
   and sysdate <  
       to_date(to_char(sysdate, 'yyyy-mm-dd ') || '18:00:00', 'yyyy-mm-dd hh24:mi:ss'))

14.存储过程中执行ddl语句:

Create Or Replace Procedure My_Proc As
Sqlddl Varchar2(1000);
Begin
Sqlddl := 'create table MyTable(ID Number(5), Name Varchar2(20))';
Dbms_Output.Put_Line(Sqlddl);
Execute Immediate Sqlddl;
End;