Oracle教程之Oracle管理数据字典（二）--Oracle数据字典的应用

1、对象定义
当执行CREATE命令建立对象时，Oracle会将对象定义存放到数据字典中。
03:31:40 SQL> select dbms_metadata.get_ddl('TABLE','DEPT') DDL FROM DUAL;
DDL
--------------------------------------------------------------------------------
CREATE TABLE "SCOTT"."DEPT"
( "DEPTNO" NUMBER(2,0),
"DNAME" VARCHAR2(14
2、查看对象占用的空间
03:36:48 SQL> conn scott/tiger
Connected.
03:37:38 SQL> select bytes from user_segments where segment_name='EMP';
BYTES
----------
65536
查看段的存储：
03:40:41 SQL> analyze table emp compute statistics;
Table analyzed.
03:40:50 SQL> select empty_blocks,blocks from user_tables;
EMPTY_BLOCKS BLOCKS
------------ ----------
0 5
3 5
0 0
0 5
0 5
6 rows selected.
03:41:08 SQL> select empty_blocks,blocks from user_tables
03:41:20 2 where table_name='EMP';
EMPTY_BLOCKS BLOCKS
------------ ----------
3 5
3、查看列信息
03:45:14 SQL> col column_name format a15
03:45:17 SQL> col data_type for a15
03:45:26 SQL> col data_default for a15
03:46:05 SQL> select column_name,data_type,data_default
03:46:14 2 from user_tab_columns
03:46:23 3 where table_name='DEPT';
COLUMN_NAME DATA_TYPE DATA_DEFAULT
--------------- --------------- ---------------
DEPTNO NUMBER
DNAME VARCHAR2
LOC VARCHAR2
4、查看约束信息
03:52:29 SQL> select a.constraint_name,a.constraint_type,b.column_name,b.position
2 from user_constraints a ,user_cons_columns b
3* where a.constraint_name=b.constraint_name and b.table_name='EMP'
CONSTRAINT_NAME CONSTRAINT_TYPE COLUMN_NAME POSITION
------------------------------ --------------- --------------- ----------
FK_DEPTNO R DEPTNO 1
PK_EMP P EMPNO 1
5、查看用户名、权限、角色
4:20:02 SQL> select username,granted_role from user_role_privs;
USERNAME GRANTED_ROLE
------------------------------ ------------------------------
PUBLIC PLUSTRACE
SCOTT CONNECT
SCOTT RESOURCE