dictionary 全部數據字典表的名稱和解釋，它有一個同義詞dict，dict_column 全部數據字典表里字段名稱和解釋
如果我們想查詢跟索引有關的數據字典時，可以用下面這條SQL語句:
select * from dictionary where instr(comments,'index')>0;
如果我們想知道user_indexes表各字段名稱的詳細含義，可以用下面這條SQL語句:
select column_name,comments from dict_columns where table_name='USER_INDEXES';
依此類推，就可以輕松知道數據字典的詳細名稱和解釋，不用查看ORACLE的其它文檔資料了。
下面按類別列出一些ORACLE用戶常用數據字典的查詢使用方法。
1、用戶
查看當前用戶的缺省表空間
select username,default_tablespace from user_users;
查看當前用戶的角色
select * from user_role_privs;
查看當前用戶的系統權限和表級權限
select * from user_sys_privs;
select * from user_tab_privs;
2、表
查看用戶下所有的表
select * from user_tables;
查看名稱包含log字符的表
select object_name,object_id from user_objects where instr(object_name,'LOG')>0;
查看某表的創建時間
select object_name,created from user_objects where object_name=upper('&table_name');
查看某表的大小
select sum(bytes)/(1024*1024) as "size(M)" from user_segments where segment_name=upper('&table_name');
查看放在ORACLE的內存區里的表
select table_name,cache from user_tables where instr(cache,'Y')>0;
3、索引
查看索引個數和類別
select index_name,index_type,table_name from user_indexes order by table_name;
查看索引被索引的字段
select * from user_ind_columns where index_name=upper('&index_name');
查看索引的大小
select sum(bytes)/(1024*1024) as "size(M)" from user_segments
where segment_name=upper('&index_name');
4、序列號
查看序列號，last_number是當前值
select * from user_sequences;
5、視圖
查看視圖的名稱
select view_name from user_views;
查看創建視圖的select語句
set view_name,text_length from user_views;
set long 2000; 說明：可以根據視圖的text_length值設定set long 的大小
select text from user_views where view_name=upper('&view_name');
6、同義詞
查看同義詞的名稱
select * from user_synonyms;
7、約束條件
查看某表的約束條件
select constraint_name, constraint_type,search_condition, r_constraint_name
from user_constraints where table_name = upper('&table_name');
select c.constraint_name,c.constraint_type,cc.column_name
from user_constraints c,user_cons_columns cc
where c.owner = upper('&table_owner') and c.table_name = upper('&table_name')
and c.owner = cc.owner and c.constraint_name = cc.constraint_name
order by cc.position;
8、存儲函數和過程
查看函數和過程的狀態
select object_name,status from user_objects where object_type='FUNCTION';
select object_name,status from user_objects where object_type='PROCEDURE';
查看函數和過程的源代碼
select text from all_source where owner=user and name=upper('&plsql_name');
查看數據庫的SQL
1、查看表空間的名稱及大小
select t.tablespace_name, round(sum(bytes/(1024*1024)),0) ts_size
from dba_tablespaces t, dba_data_files d
where t.tablespace_name = d.tablespace_name
group by t.tablespace_name;
2、查看表空間物理文件的名稱及大小
select tablespace_name, file_id, file_name,
round(bytes/(1024*1024),0) total_space
from dba_data_files
order by tablespace_name;
3、查看回滾段名稱及大小
select segment_name, tablespace_name, r.status,
(initial_extent/1024) InitialExtent,(next_extent/1024) NextExtent,
max_extents, v.curext CurExtent
From dba_rollback_segs r, v$rollstat v
Where r.segment_id = v.usn(+)
order by segment_name ;
4、查看控制文件
select name from v$controlfile;
5、查看日志文件
select member from v$logfile;
6、查看表空間的使用情況
select sum(bytes)/(1024*1024) as free_space,tablespace_name
from dba_free_space group by tablespace_name;
SELECT A.TABLESPACE_NAME,A.BYTES TOTAL,B.BYTES USED, C.BYTES FREE,
(B.BYTES*100)/A.BYTES "% USED",(C.BYTES*100)/A.BYTES "% FREE"
FROM SYS.SM$TS_AVAIL A,SYS.SM$TS_USED B,SYS.SM$TS_FREE C
WHERE A.TABLESPACE_NAME=B.TABLESPACE_NAME AND A.TABLESPACE_NAME=C.TABLESPACE_NAME;
7、查看數據庫庫對象
select owner, object_type, status, count(*) count# from all_objects group by owner, object_type, status;
8、查看數據庫的版本
Select version FROM Product_component_version
Where SUBSTR(PRODUCT,1,6)='Oracle';
9、查看數據庫的創建日期和歸檔方式
Select Created, Log_Mode, Log_Mode From V$Database;
ORACLE用戶連接的管理用系統管理員，
查看當前數據庫有幾個用戶連接：
select username,sid,serial# from v$session;
如果要停某個連接用
alter system kill session 'sid,serial#';
如果這命令不行,找它UNIX的進程數
select pro.spid from v$session ses,v$process pro where ses.sid=21 and ses.paddr=pro.addr;
說明：21是某個連接的sid數然后用 kill 命令殺此進程號