select    nvl(ses.USERNAME,'ORACLE PROC') username,
    OSUSER os_user,
    PROCESS pid,
    ses.SID sid,
    SERIAL#,
    PHYSICAL_READS,
    BLOCK_GETS,
    CONSISTENT_GETS,
    BLOCK_CHANGES,
    CONSISTENT_CHANGES
from    v$session ses,
    v$sess_io sio
where     ses.SID = sio.SID
order     by PHYSICAL_READS, ses.USERNAME;


select  nvl(ss.USERNAME,'ORACLE PROC') username,
    se.SID,
    sn.NAME stastic,
    VALUE usage
from     v$session ss,
    v$sesstat se,
    v$statname sn
where      se.STATISTIC# = sn.STATISTIC#
and      se.SID = ss.SID
and    se.VALUE > 0
order      by sn.NAME, se.SID, se.VALUE desc;

select * from v$session;  --489 491 484


select    nvl(ses.USERNAME,'ORACLE PROC') username,
    OSUSER os_user,
    PROCESS pid,
    ses.SID sid,
    SERIAL#,
    PHYSICAL_READS,
    BLOCK_GETS,
    CONSISTENT_GETS,
    BLOCK_CHANGES,
    CONSISTENT_CHANGES
from    v$session ses,
    v$sess_io sio
where     ses.SID = sio.SID
order     by PHYSICAL_READS, ses.USERNAME;

select * from v$session where suser = 'rmai';

SELECT s.inst_id,
       s.sid,
       s.serial#,
       p.spid,
       s.username,
       s.program
FROM   gv$session s
       JOIN gv$process p ON p.addr = s.paddr AND p.inst_id = s.inst_id
WHERE  s.type != 'BACKGROUND'
and SID in (484,
491,
499,
531);

--Find out the running sql script
SELECT SE.sid, SE.serial#, PR.spid, SE.status, SUBSTR(SE.program, 1, 10) PROG,
  SUBSTR(SE.machine, 1, 10) MACH,
  SQ.sql_text
FROM v$session SE, v$sqlarea SQ, v$process PR
WHERE SE.paddr = PR.ADDR(+)
  AND SE.sql_address = SQ.address(+)
  AND schemaname <> 'SYS'
ORDER BY SE.sid;


--Find out the lock table
select c.owner, c.object_name, c.object_type, b.sid, b.serial#, b.status, b.osuser, b.machine, b.logon_time, vp.spid
from v$locked_object a , v$session b,  dba_objects c, v$process  vp
where b.sid = a.session_id and vp.addr=b.paddr and a.object_id = c.object_id;


--Kill session
alter system kill session 'sid,serial#' ;


--Check Users
select
  username,
  osuser,
  terminal
--  utl_inaddr.get_host_address(terminal) IP_ADDRESS
from
  v$session
where
  username is not null
order by
  username,
  osuser;

select a.constraint_name, a.table_name, b.constraint_name 
from user_constraints a, user_constraints b
where a.constraint_type = 'R' 
and b.constraint_type = 'P' 
and a.r_constraint_name = b.constraint_name

P 代表主键
R 代表外键

通过关联，能查询到你所想要的一切。

 

select constraint_name from dba_cons_columns where table_name='';
Alter table XX drop constraint sys…

/////////////////////////////

user_constraints,user_cons_columns查看外键

Oracle 查看一个表对应的主键和外键的约束关系，查看的语句：

select a.owner 主键拥有者

         ,a.table_name 主键表

        ,b.column_name 主键列

        ,C.OWNER 外键拥有者

        ,c.table_name 外键表

       ,d.column_name 外键列
from user_constraints a
left join user_cons_columns b

            on a.constraint_name=b.constraint_name
left join user_constraints C

            ON C.R_CONSTRAINT_NAME=a.constraint_name
left join user_cons_columns d

            on c.constraint_name=d.constraint_name
where a.constraint_type='P'

    and a.table_name='XXX' --需要查看主外键关系的表
order by a.table_name

宁外的一种写法

select
a.owner 外键拥有者,
a.table_name 外键表,
substr(c.column_name,1,127) 外键列,
b.owner 主键拥有者,
b.table_name 主键表,
substr(d.column_name,1,127) 主键列
from
user_constraints a,
user_constraints b,
user_cons_columns c,
user_cons_columns d
where
    a.r_constraint_name=b.constraint_name
and a.constraint_type='R'
and b.constraint_type='P'
and a.r_owner=b.owner
and a.constraint_name=c.constraint_name
and b.constraint_name=d.constraint_name
and a.owner=c.owner
and a.table_name=c.table_name
and b.owner=d.owner
and b.table_name=d.table_name

数据字典表列说明：

desc user_constraints

Name Comments
OWNER 表的所有者
CONSTRAINT_NAME 约束名
CONSTRAINT_TYPE 约束类型
TABLE_NAME Name associated with table with constraint definition
SEARCH_CONDITION Text of search condition for table check
R_OWNER Owner of table used in referential constraint
R_CONSTRAINT_NAME Name of unique constraint definition for referenced table
DELETE_RULE The delete rule for a referential constraint
STATUS Enforcement status of constraint - ENABLED or DISABLED
DEFERRABLE Is the constraint deferrable - DEFERRABLE or NOT DEFERRABLE
DEFERRED Is the constraint deferred by default - DEFERRED or IMMEDIATE
VALIDATED Was this constraint system validated? - VALIDATED or NOT VALIDATED
GENERATED Was the constraint name system generated? - GENERATED NAME or USERNAME
BAD Creating this constraint should give ORA-02436. Rewrite it before2000 AD.
RELY If set, this flag will be used in optimizer
LAST_CHANGE The date when this column was last enabled or disabled
INDEX_OWNER The owner of the index used by the constraint
INDEX_NAME The index used by the constraint
INVALID  
VIEW_RELATED  

desc user_cons_columns;

Name Default Comments
OWNER Owner of the constraint definition
CONSTRAINT_NAME Name associated with the constraint definition
TABLE_NAME Name associated with table with constraint definition
COLUMN_NAME Name associated with column or attribute of object column specified in the constraint definition
POSITION Original position of column or attribute in definition

 

http://blog.csdn.net/maqinqin/archive/2009/05/26/4217045.aspx

desc   后发现
user_constraints是表约束的视图,描述的是约束类型(constraint_type)是什么,属于哪些表(table_name),如 果约束的类型为R(外键)的话,那么r_constraint_name字段存放的就是被引用主表中的主键约束名。   
user_cons_columns是表约束字段的视图,说明表中的和约束相关的列参与了哪些约束。这些约束有主键约束,外键约束,索引约束.
两者可以通过(owner,constraint_name,table_name)关联

select
a.owner 外键拥有者,
a.table_name 外键表,
substr(c.column_name,1,127) 外键列,
b.owner 主键拥有者,
b.table_name 主键表,
substr(d.column_name,1,127) 主键列
from
user_constraints a,
user_constraints b,
user_cons_columns c,
user_cons_columns d
where
    a.r_constraint_name=b.constraint_name
and a.constraint_type='R'
and b.constraint_type='P'
and a.r_owner=b.owner
and a.constraint_name=c.constraint_name
and b.constraint_name=d.constraint_name
and a.owner=c.owner
and a.table_name=c.table_name
and b.owner=d.owner
and b.table_name=d.table_name

数据字典表列说明：

desc user_constraints

Name                                      

http://www.blogjava.net/sunzhong/articles/289139.html

 

/////////////////////////////////////

 

Oracle 查看一个表对应的主键和外键的约束关系，查看的语句：

select a.owner 主键拥有者

         ,a.table_name 主键表

        ,b.column_name 主键列

        ,C.OWNER 外键拥有者

        ,c.table_name 外键表

       ,d.column_name 外键列
from user_constraints  a
left join user_cons_columns b

            on  a.constraint_name=b.constraint_name
left join user_constraints C

            ON C.R_CONSTRAINT_NAME=a.constraint_name
left join user_cons_columns d

            on c.constraint_name=d.constraint_name
where  a.constraint_type='P'

    and  a.table_name='XXX' --需要查看主外键关系的表
order by a.table_name

宁外的一种写法

select
a.owner 外键拥有者,
a.table_name 外键表,
substr(c.column_name,1,127) 外键列,
b.owner 主键拥有者,
b.table_name 主键表,
substr(d.column_name,1,127) 主键列
from
user_constraints a,
user_constraints b,
user_cons_columns c,
user_cons_columns d
where
    a.r_constraint_name=b.constraint_name
and a.constraint_type='R'
and b.constraint_type='P'
and a.r_owner=b.owner
and a.constraint_name=c.constraint_name
and b.constraint_name=d.constraint_name
and a.owner=c.owner
and a.table_name=c.table_name
and b.owner=d.owner
and b.table_name=d.table_name

数据字典表列说明：

desc user_constraints

 

Name	Comments
OWNER	表的所有者
CONSTRAINT_NAME	约束名
CONSTRAINT_TYPE	约束类型
TABLE_NAME	Name associated with table with constraint definition
SEARCH_CONDITION	Text of search condition for table check
R_OWNER	Owner of table used in referential constraint
R_CONSTRAINT_NAME	Name of unique constraint definition for referenced table
DELETE_RULE	The delete rule for a referential constraint
STATUS	Enforcement status of constraint -  ENABLED or DISABLED
DEFERRABLE	Is the constraint deferrable - DEFERRABLE or NOT DEFERRABLE
DEFERRED	Is the constraint deferred by default -  DEFERRED or IMMEDIATE
VALIDATED	Was this constraint system validated? -  VALIDATED or NOT VALIDATED
GENERATED	Was the constraint name system generated? -  GENERATED NAME or USERNAME
BAD	Creating this constraint should give ORA-02436.  Rewrite it before2000 AD.
RELY	If set, this flag will be used in optimizer
LAST_CHANGE	The date when this column was last enabled or disabled
INDEX_OWNER	The owner of the index used by the constraint
INDEX_NAME	The index used by the constraint
INVALID
VIEW_RELATED

desc user_cons_columns;

 

Name	Default Comments
OWNER	Owner of the constraint definition
CONSTRAINT_NAME	Name associated with the constraint definition
TABLE_NAME	Name associated with table with constraint definition
COLUMN_NAME	Name associated with column or attribute of object column specified in the constraint definition
POSITION	Original position of column or attribute in definition

总体解释：
DML（data manipulation language）：
       它们是SELECT、UPDATE、INSERT、DELETE，就象它的名字一样，这4条命令是用来对数据库里的数据进行操作的语言
DDL（data definition language）：
       DDL比DML要多，主要的命令有CREATE、ALTER、DROP等，DDL主要是用在定义或改变表（TABLE）的结构，数据类型，表之间的链接和约束等初始化工作上，他们大多在建立表时使用
DCL（Data Control Language）：
       是数据库控制功能。是用来设置或更改数据库用户或角色权限的语句，包括（grant,deny,revoke等）语句。在默认状态下，只有sysadmin,dbcreator,db_owner或db_securityadmin等人员才有权力执行DCL

详细解释：
一、DDL is Data Definition Language statements. Some examples:数据定义语言，用于定义和管理 SQL 数据库中的所有对象的语言
      1.CREATE - to create objects in the database   创建
      2.ALTER - alters the structure of the database   修改
      3.DROP - delete objects from the database   删除
      4.TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
      TRUNCATE TABLE [Table Name]。
　　下面是对Truncate语句在MSSQLServer2000中用法和原理的说明：
　　Truncate table 表名 速度快,而且效率高,因为:
　　TRUNCATE TABLE 在功能上与不带 WHERE 子句的 DELETE 语句相同：二者均删除表中的全部行。但 TRUNCATE TABLE 比 DELETE 速度快，且使用的系统和事务日志资源少。
　　DELETE 语句每次删除一行，并在事务日志中为所删除的每行记录一项。TRUNCATE TABLE 通过释放存储表数据所用的数据页来删除数据，并且只在事务日志中记录页的释放。
　　TRUNCATE TABLE 删除表中的所有行，但表结构及其列、约束、索引等保持不变。新行标识所用的计数值重置为该列的种子。如果想保留标识计数值，请改用 DELETE。如果要删除表定义及其数据，请使用 DROP TABLE 语句。
　　对于由 FOREIGN KEY 约束引用的表，不能使用 TRUNCATE TABLE，而应使用不带 WHERE 子句的 DELETE 语句。由于 TRUNCATE TABLE 不记录在日志中，所以它不能激活触发器。
　　TRUNCATE TABLE 不能用于参与了索引视图的表。
       5.COMMENT - add comments to the data dictionary 注释
       6.GRANT - gives user's access privileges to database 授权
       7.REVOKE - withdraw access privileges given with the GRANT command   收回已经授予的权限

二、DML is Data Manipulation Language statements. Some examples:数据操作语言，SQL中处理数据等操作统称为数据操纵语言
       1.SELECT - retrieve data from the a database           查询
       2.INSERT - insert data into a table                    添加
        3.UPDATE - updates existing data within a table    更新
       4.DELETE - deletes all records from a table, the space for the records remain   删除
       5.CALL - call a PL/SQL or Java subprogram
       6.EXPLAIN PLAN - explain access path to data
       Oracle RDBMS执行每一条SQL语句，都必须经过Oracle优化器的评估。所以，了解优化器是如何选择(搜索)路径以及索引是如何被使用的，对优化SQL语 句有很大的帮助。Explain可以用来迅速方便地查出对于给定SQL语句中的查询数据是如何得到的即搜索路径(我们通常称为Access Path)。从而使我们选择最优的查询方式达到最大的优化效果。
       7.LOCK TABLE - control concurrency 锁，用于控制并发

三、DCL is Data Control Language statements. Some examples:数据控制语言，用来授予或回收访问数据库的某种特权，并控制数据库操纵事务发生的时间及效果，对数据库实行监视等
       1.COMMIT - save work done 提交
        2.SAVEPOINT - identify a point in a transaction to which you can later roll back 保存点
       3.ROLLBACK - restore database to original since the last COMMIT   回滚
       4.SET TRANSACTION - Change transaction options like what rollback segment to use   设置当前事务的特性，它对后面的事务没有影响．



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