数据字典

 

二．数据字典

 

Oracle数据字典是有表和视图组成，存储有关数据库结构信息的一些数据库对象。数据库字典描述了实际数据是如何组织的。比如一个表的创建者信息，创建时间信息，所属表空间信息，用户访问权限信息等。对它们可以象处理其他数据库表或视图一样进行查询，但不能进行任何修改。它们存放在SYSTEM表空间中，当用户在对数据库中的数据进行操作时遇到困难就可以访问数据字典来查看详细的信息。用户可以用SQL语句访问数据库数据字典。

 

Oracle数据库字典通常是在创建和安装数据库时被创建的，Oracle数据字典是Oracle数据库系统工作的基础，没有数据字典的支持，Oracle数据库系统就不能进行任何工作。数据字典中的表是不能直接被访问的，但是可以访问数据字典中的视图。

 

 

2.1 数据字典内容包括：

1,数据库中所有模式对象的信息，如表、视图、簇、及索引等。

2,分配多少空间，当前使用了多少空间等。

3,列的缺省值。

4,约束信息的完整性。

5,Oracle用户的名字。

6,用户及角色被授予的权限。

7,用户访问或使用的审计信息。

8,其它产生的数据库信息。

 

2.2  数据字典分为 数据字典表 和 数据字典视图

2.2. 1 数据字典表

       数据字典表里的数据是Oracle系统存放的系统数据，而普通表存放的是用户的数据。为了方便的区别这些表，这些表的名字都是用"$"结尾，这些表属于SYS用户。

       数据字典表由$ORACLE_HOME/rdbms/admin/sql.bsq 脚本创建， 这个脚本里又调用了其他的脚本来创建这些数据字典表。 在那些创建脚本里有基表的创建SQL。 感兴趣的自己打开看看。

 

       Oracle 对数据字典表的说明：

       These underlying tables store information about the database. Only Oracle Database should write to and read these tables. Users rarely access the base tables directly because they are normalized and most data is stored in a cryptic format.

 

       这些数据字典表，只有Oracle 能够进行读写。

 

       SYS用户下的这些数据字典表，存放在system 表空间下面，表名都用"$"结尾，为了便于用户对数据字典表的查询， Oracle对这些数据字典都分别建立了用户视图，这样即容易记住，还隐藏了数据字典表表之间的关系，Oracle针对这些对象的范围，分别把视图命名为DBA_XXXX, ALL_XXXX和USER_XXXX。

      

       关于这3类视图，下面有介绍。

 

       Oracle为了便于汇总数据字典表的信息，把所有的数据字典都汇集到dictionary表里了，通过对这个表的查询，我们可以很方便的找到数据库提供的数据字典。

 

2.2.2  数据字典视图

       动态性能视图由脚本：$ORACLE_HOME/rdbms/admin/catalog.sql 创建， 该脚本也只是一个总的调用，在该脚本里由调用了其他的脚本。 感兴趣的可以自己打开看一下，在那些脚本里，可以看到视图的创建SQL.

       这是因为这个脚本会创建动态视图，所以在做DB 升级的时候，也需要执行这个脚本，重新创建视图。

 

       数据字典视图分2类：静态数据字典（静态性能视图） 和 动态数据字典（动态性能视图）

 

2.2.2.1 静态数据字典（静态性能视图）

       静态数据字典中的视图分为三类，它们分别由三个前缀够成：user_*、 all_*、 dba_*。

user_*：该视图存储了关于当前用户所拥有的对象的信息。（即所有在该用户模式下的对象）

all_*：该试图存储了当前用户能够访问的对象的信息, 而不是当前用户拥有的对象。（与user_*相比，all_* 并不需要拥有该对象，只需要具有访问该对象的权限即可）

dba_*：该视图存储了数据库中所有对象的信息。（前提是当前用户具有访问这些数据库的权限，一般来说必须具有管理员权限）

 

       这些视图由SYS用户创建的，所以使用需要加上SYS,为了方便， Oracle为每个数据字典表的视图头建立了同名字的公共同义词(public synonyms). 这样简单的处理就省去了写sys.的麻烦。

 

 

示例：

（1）user_tables：主要描述当前用户拥有的所有表的信息，主要包括表名、表空间名、簇名等。通过此视图可以清楚了解当前用户可以操作的表有哪些。

SQL>select * from user_tables;

       （2）user_indexes： 查询该用户拥有哪些索引。

SQL>select index_name from user_indexes;

       （3）user_views： 查询该用户拥有哪些视图

SQL>select view_name from user_views;

       （4）user_objects：查询该用户拥有哪些数据库对象,对象包括表、视图、存储过程、触发器、包、索引、序列、JAVA文件等。

SQL>select object_name from user_objects;

       （5）user_users：主要描述当前用户的信息，主要包括当前用户名、帐户id、帐户状态、表空间名、创建时间等。

SQL>select * from user_users;

       （6）all_objects：查询某一用户下的所有表、过程、函数等信息。

SQL>select owner , object_name ,object_type from all_objects

 

 

2.2.2.2  动态数据字典（动态性能视图）

       除了静态数据字典中三类视图，其他的字典视图中主要的是V$视图，之所以这样叫是因为他们都是以V$或GV$开头的。这些视图会不断的进行更新，从而提供了关于内存和磁盘的运行情况，所以我们只能对其进行只读访问而不能修改它们。

 

Throughout its operation, Oracle Database maintains a set of virtual tables that record current database activity. These views are called dynamic performance views because they are continuously updated while a database is open and in use. The views, also sometimes called V$ views。

 

V$视图是基于X$虚拟视图的。V$视图是SYS用户所拥有的，在缺省状况下，只有SYS用户和拥有DBA系统权限的用户可以看到所有的视图，没有DBA权限的用户可以看到USER_和ALL_视图，但不能看到DBA_视图。与DBA_,ALL,和USER_视图中面向数据库信息相反，这些视图可视的给出了面向实例的信息。      

       动态性能表用于记录当前数据库的活动，只存于数据库运行期间，实际的信息都取自内存和控制文件。 DBA可以使用动态视图来监视和调节数据。

 

关于动态性能视图，参考：

       Oracle 动态性能视图

       http://blog.csdn.net/tianlesoftware/archive/2010/09/04/5863191.aspx

 

 

2.3 视图家族

 

在Oracle的绝大多数数据字典视图中都有象DBA_TABLES,ALL_TABLES和USER_TABLES这样的视图家族。Oracle中有超过100个视图家族，下表列出了最重要和最常用的视图家族，需要注意的是每个视图家族都有一个DBA_,一个ALL_ 和一个USER_视图。

 

 

视图家族	描述
COL_PRIVS	包含了表的列权限，包括授予者、被授予者和权限
EXTENTS	数据范围信息，比如数据文件，数据段名(segment_name)和大小
INDEXES	索引信息，比如类型、唯一性和被涉及的表
IND_COLUMNS	索引列信息，比如索引上的列的排序方式
OBJECTS	对象信息，比如状态和DDL time
ROLE_PRIVS	角色权限，比如GRANT和ADMIN选项
SEGMENTS	表和索引的数据段信息，比如tablespace和storage
SEQUECNCES	序列信息，比如序列的cache、cycle和ast_number
SOURCE	除触发器之外的所有内置过程、函数、包的源代码
SYNONYMS	别名信息，比如引用的对象和数据库链接db_link
SYS_PRIVS	系统权限，比如grantee、privilege、admin选项
TAB_COLUMNS	表和视图的列信息，包括列的数据类型
TAB_PRIVS	表权限，比如授予者、被授予者和权限
TABLES	表信息，比如表空间(tablespace),存储参数(storage parms)和数据行的数量
TRIGGERS	触发器信息，比如类型、事件、触发体(trigger body)
USERS	用户信息，比如临时的和缺省的表空间
VIEWS	视图信息，包括视图定义

 

 

在Oracle中还有一些不常用的数据字典表，但这些表不是真正的字典家族，他们都是一些重要的单一的视图。这些视图见下表:

 

 

视图名称	描述
USER_COL_PRIVS_MADE	用户授予他人的列权限
USER_COL_PRIVS_RECD	用户获得的列权限
USER_TAB_PRIVS_MADE	用户授予他人的表权限
USER_TAB_PRIVS_RECD	用户获得的表权限

 

 

 

2.4 查看数据字典

       我们通过dictionary 字典来查看所有的视图和其描述。 该表只有2个字段：表名和描述

      

SQL> desc dictionary

 名称                                      是否为空? 类型

 ----------------------------------------- -------- -------------------------

 TABLE_NAME                                         VARCHAR2(30)

 COMMENTS                                           VARCHAR2(4000)

 

我们可以用以下SQL来查看所有数据字典对象：

SQL>select * from dictionary;

 

Oracle 11g中有2592个对象。

SQL> select count(*) from dictionary;

COUNT(*)

----------

2592

 

部分数据如下表：

视图名	描述
ALL_CATALOG	All tables, views, synonyms, sequences accessible to the user
ALL_COL_COMMENTS	Comments on columns of accessible tables and views
ALL_COL_GRANTS_MADE	Grants on columns for which the user is owner or grantor
ALL_COL_GRANTS_RECD	Grants on columns for which the user or PUBLIC is the grantee
ALL_COL_PRIVS	Grants on columns for which the user is the grantor, grantee, owner, or an enabled role or PUBLIC is the grantee
ALL_COL_PRIVS_MADE	Grants on columns for which the user is owner or grantor
ALL_COL_PRIVS_RECD	Grants on columns for which the user, PUBLIC or enabled role is the grantee
ALL_CONSTRAINTS	Constraint definitions on accessible tables
ALL_CONS_COLUMNS	Information about accessible columns in constraint definitions
ALL_DB_LINKS	Database links accessible to the user
ALL_DEF_AUDIT_OPTS	Auditing options for newly created objects
ALL_DEPENDENCIES	Dependencies to and from objects accessible to the user
ALL_ERRORS	Current errors on stored objects that user is allowed to create
ALL_INDEXES	Descriptions of indexes on tables accessible to the user
ALL_IND_COLUMNS	COLUMNs comprising INDEXes on accessible TABLES
ALL_OBJECTS	Objects accessible to the user
ALL_REFRESH	All the refresh groups that the user can touch
ALL_REFRESH_CHILDREN	All the objects in refresh groups, where the user can touch the group
ALL_SEQUENCES	Description of SEQUENCEs accessible to the user
ALL_SNAPSHOTS	Snapshots the user can look at
ALL_SOURCE	Current source on stored objects that user is allowed to create
ALL_SYNONYMS	All synonyms accessible to the user
ALL_TABLES	Description of tables accessible to the user
ALL_TAB_COLUMNS	Columns of all tables, views and clusters
ALL_TAB_COMMENTS	Comments on tables and views accessible to the user
ALL_TAB_GRANTS_MADE	User's grants and grants on user's objects
ALL_TAB_GRANTS_RECD	Grants on objects for which the user or PUBLIC is the grantee
ALL_TAB_PRIVS	Grants on objects for which the user is the grantor, grantee, owner, or an enabled role or PUBLIC is the grantee
ALL_TAB_PRIVS_MADE	User's grants and grants on user's objects
ALL_TAB_PRIVS_RECD	Grants on objects for which the user, PUBLIC or enabled role is the grantee
ALL_TRIGGERS	Triggers accessible to the current user
ALL_TRIGGER_COLS	Column usage in user's triggers or in triggers on user's tables
ALL_USERS	Information about all users of the database
ALL_VIEWS	Text of views accessible to the user
USER_AUDIT_CONNECT	Audit trail entries for user logons/logoffs
USER_AUDIT_OBJECT	Audit trail records for statements concerning objects, specifically: table, cluster, view, index, sequence, [public] database link, [public] synonym, procedure, trigger, rollback segment, tablespace, role, user
USER_AUDIT_SESSION
USER_AUDIT_STATEMENT	Audit trail records concerning grant, revoke, audit, noaudit and alter system
USER_AUDIT_TRAIL	Audit trail entries relevant to the user
USER_CATALOG	Tables, Views, Synonyms and Sequences owned by the user
USER_CLUSTERS	Descriptions of user's own clusters
USER_CLU_COLUMNS	Mapping of table columns to cluster columns
USER_COL_COMMENTS	Comments on columns of user's tables and views
USER_COL_GRANTS	Grants on columns for which the user is the owner, grantor or grantee
USER_COL_GRANTS_MADE	All grants on columns of objects owned by the user
USER_COL_GRANTS_RECD	Grants on columns for which the user is the grantee
USER_COL_PRIVS	Grants on columns for which the user is the owner, grantor or grantee
USER_COL_PRIVS_MADE	All grants on columns of objects owned by the user
USER_COL_PRIVS_RECD	Grants on columns for which the user is the grantee
USER_CONSTRAINTS	Constraint definitions on user's own tables
USER_CONS_COLUMNS	Information about accessible columns in constraint definitions
USER_CROSS_REFS	Cross references for user's views and synonyms
USER_DB_LINKS	Database links owned by the user
USER_DEPENDENCIES	Dependencies to and from a users objects
USER_ERRORS	Current errors on stored objects owned by the user
USER_EXTENTS	Extents comprising segments owned by the user
USER_FREE_SPACE	Free extents in tablespaces accessible to the user
USER_INDEXES	Description of the user's own indexes
USER_IND_COLUMNS	COLUMNs comprising user's INDEXes or on user's TABLES
USER_JOBS	All jobs owned by this user
USER_OBJECTS	Objects owned by the user
USER_OBJECT_SIZE	Sizes, in bytes, of various pl/sql objects
USER_OBJ_AUDIT_OPTS	Auditing options for user's own tables and views
USER_REFRESH	All the refresh groups
USER_REFRESH_CHILDREN	All the objects in refresh groups, where the user owns the refresh group
USER_RESOURCE_LIMITS	Display resource limit of the user
USER_ROLE_PRIVS	Roles granted to current user
USER_SEGMENTS	Storage allocated for all database segments
USER_SEQUENCES	Description of the user's own SEQUENCEs
USER_SNAPSHOTS	Snapshots the user can look at
USER_SNAPSHOT_LOGS	All snapshot logs owned by the user
USER_SOURCE	Source of stored objects accessible to the user
USER_SYNONYMS	The user's private synonyms
USER_SYS_PRIVS	System privileges granted to current user
USER_TABLES	Description of the user's own tables
USER_TABLESPACES	Description of accessible tablespaces
USER_TAB_AUDIT_OPTS	Auditing options for user's own tables and views
USER_TAB_COLUMNS	Columns of user's tables, views and clusters
USER_TAB_COMMENTS	Comments on the tables and views owned by the user
USER_TAB_GRANTS	Grants on objects for which the user is the owner, grantor or grantee
USER_TAB_GRANTS_MADE	All grants on objects owned by the user
USER_TAB_GRANTS_RECD	Grants on objects for which the user is the grantee
USER_TAB_PRIVS	Grants on objects for which the user is the owner, grantor or grantee
USER_TAB_PRIVS_MADE	All grants on objects owned by the user
USER_TAB_PRIVS_RECD	Grants on objects for which the user is the grantee
USER_TRIGGERS	Triggers owned by the user
USER_TRIGGER_COLS	Column usage in user's triggers
USER_TS_QUOTAS	Tablespace quotas for the user
USER_USERS	Information about the current user
USER_VIEWS	Text of views owned by the user
AUDIT_ACTIONS	Description table for audit trail action type codes. Maps action type numbers to action type names
COLUMN_PRIVILEGES	Grants on columns for which the user is the grantor, grantee, owner, or an enabled role or PUBLIC is the grantee
DICTIONARY	Description of data dictionary tables and views
DICT_COLUMNS	Description of columns in data dictionary tables and views
DUAL
GLOBAL_NAME	global database name
INDEX_HISTOGRAM	statistics on keys with repeat count
INDEX_STATS	statistics on the b-tree
RESOURCE_COST	Cost for each resource
ROLE_ROLE_PRIVS	Roles which are granted to roles
ROLE_SYS_PRIVS	System privileges granted to roles
ROLE_TAB_PRIVS	Table privileges granted to roles
SESSION_PRIVS	Privileges which the user currently has set
SESSION_ROLES	Roles which the user currently has enabled.
TABLE_PRIVILEGES	Grants on objects for which the user is the grantor, grantee, owner, or an enabled role or PUBLIC is the grantee
ACCESSIBLE_COLUMNS	Synonym for ALL_TAB_COLUMNS
ALL_COL_GRANTS	Synonym for COLUMN_PRIVILEGES
ALL_JOBS	Synonym for USER_JOBS
ALL_TAB_GRANTS	Synonym for TABLE_PRIVILEGES
CAT	Synonym for USER_CATALOG
CLU	Synonym for USER_CLUSTERS
COLS	Synonym for USER_TAB_COLUMNS
DBA_AUDIT_CONNECT	Synonym for USER_AUDIT_CONNECT
DBA_AUDIT_RESOURCE	Synonym for USER_AUDIT_RESOURCE
DBA_REFRESH_CHILDREN	Synonym for USER_REFRESH_CHILDREN
DICT	Synonym for DICTIONARY
IND	Synonym for USER_INDEXES
OBJ	Synonym for USER_OBJECTS
SEQ	Synonym for USER_SEQUENCES
SM$VERSION	Synonym for SM_$VERSION
SYN	Synonym for USER_SYNONYMS
TABS	Synonym for USER_TABLES
V$ACCESS	Synonym for V_$ACCESS
V$ARCHIVE	Synonym for V_$ARCHIVE
V$BACKUP	Synonym for V_$BACKUP
V$BGPROCESS	Synonym for V_$BGPROCESS
V$CIRCUIT	Synonym for V_$CIRCUIT
V$COMPATIBILITY	Synonym for V_$COMPATIBILITY
V$COMPATSEG	Synonym for V_$COMPATSEG
V$CONTROLFILE	Synonym for V_$CONTROLFILE
V$DATABASE	Synonym for V_$DATABASE
V$DATAFILE	Synonym for V_$DATAFILE
V$DBFILE	Synonym for V_$DBFILE
V$DBLINK	Synonym for V_$DBLINK
V$DB_OBJECT_CACHE	Synonym for V_$DB_OBJECT_CACHE
V$DISPATCHER	Synonym for V_$DISPATCHER
V$ENABLEDPRIVS	Synonym for V_$ENABLEDPRIVS
V$FILESTAT	Synonym for V_$FILESTAT
V$FIXED_TABLE	Synonym for V_$FIXED_TABLE
V$LATCH	Synonym for V_$LATCH
V$LATCHHOLDER	Synonym for V_$LATCHHOLDER
V$LATCHNAME	Synonym for V_$LATCHNAME
V$LIBRARYCACHE	Synonym for V_$LIBRARYCACHE
V$LICENSE	Synonym for V_$LICENSE
V$LOADCSTAT	Synonym for V_$LOADCSTAT
V$LOADTSTAT	Synonym for V_$LOADTSTAT
V$LOCK	Synonym for V_$LOCK
V$LOG	Synonym for V_$LOG
V$LOGFILE	Synonym for V_$LOGFILE
V$LOGHIST	Synonym for V_$LOGHIST
V$LOG_HISTORY	Synonym for V_$LOG_HISTORY
V$MLS_PARAMETERS	Synonym for V_$MLS_PARAMETERS
V$MTS	Synonym for V_$MTS
V$NLS_PARAMETERS	Synonym for V_$NLS_PARAMETERS
V$NLS_VALID_VALUES	Synonym for V_$NLS_VALID_VALUES
V$OPEN_CURSOR	Synonym for V_$OPEN_CURSOR
V$OPTION	Synonym for V_$OPTION
V$PARAMETER	Synonym for V_$PARAMETER
V$PQ_SESSTAT	Synonym for V_$PQ_SESSTAT
V$PQ_SLAVE	Synonym for V_$PQ_SLAVE
V$PQ_SYSSTAT	Synonym for V_$PQ_SYSSTAT
V$PROCESS	Synonym for V_$PROCESS
V$QUEUE	Synonym for V_$QUEUE
V$RECOVERY_LOG	Synonym for V_$RECOVERY_LOG
V$RECOVER_FILE	Synonym for V_$RECOVER_FILE
V$REQDIST	Synonym for V_$REQDIST
V$RESOURCE	Synonym for V_$RESOURCE
V$ROLLNAME	Synonym for V_$ROLLNAME
V$ROLLSTAT	Synonym for V_$ROLLSTAT
V$ROWCACHE	Synonym for V_$ROWCACHE
V$SESSION	Synonym for V_$SESSION
V$SESSION_CURSOR_CACHE	Synonym for V_$SESSION_CURSOR_CACHE
V$SESSION_EVENT	Synonym for V_$SESSION_EVENT
V$SESSION_WAIT	Synonym for V_$SESSION_WAIT
V$SESSTAT	Synonym for V_$SESSTAT
V$SESS_IO	Synonym for V_$SESS_IO
V$SGA	Synonym for V_$SGA
V$SGASTAT	Synonym for V_$SGASTAT
V$SHARED_SERVER	Synonym for V_$SHARED_SERVER
V$SQLAREA	Synonym for V_$SQLAREA
V$STATNAME	Synonym for V_$STATNAME
V$SYSSTAT	Synonym for V_$SYSSTAT
V$SYSTEM_CURSOR_CACHE	Synonym for V_$SYSTEM_CURSOR_CACHE
V$SYSTEM_EVENT	Synonym for V_$SYSTEM_EVENT
V$THREAD	Synonym for V_$THREAD
V$TIMER	Synonym for V_$TIMER
V$TRANSACTION	Synonym for V_$TRANSACTION
V$TYPE_SIZE	Synonym for V_$TYPE_SIZE
V$VERSION	Synonym for V_$VERSION
V$WAITSTAT	Synonym for V_$WAITSTAT
V$_LOCK	Synonym for V_$_LOCK