–1. 查询系统所有对象

select owner, object_name, object_type, created, last_ddl_time, timestamp, status

from dba_objects

where owner=upper('scott')

–2. 查看系统所有表

select owner, table_name, tablespace_name from dba_tables

–3. 查看所有用户的表

select owner, table_name, tablespace_name from all_tables

–4. 查看当前用户表

select table_name, tablespace_name from user_tables

–5. 查看用户表索引

select t.*,i.index_type from user_ind_columns t, user_indexes i where

t.index_name = i.index_name and t.table_name = i.table_name

and t.table_name = 要查询的表

–6. 查看主键

select cu.* from user_cons_columns cu, user_constraints au

where cu.constraint_name = au.constraint_name

and au.constraint_type = upper('p') and au.table_name = 要查询的表

–7. 查看唯一性约束

select column_name from user_cons_columns cu, user_constraints au

where cu.constraint_name = au.constraint_name and au.constraint_type =  upper('u')

and au.table_name = 要查询的表

–8. 查看外键

select * from user_constraints c where c.constraint_type = 'r' and c.table_name = 要查询的表

select * from user_cons_columns cl where cl.constraint_name = 外键名称

select * from user_cons_columns cl where cl.constraint_name = 外键引用表的键名

–9. 查看表的列属性

select t.*,c.comments

from user_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 = 要查询的表

–10. 查看所有表空间

select tablespace_name from dba_data_files group by tablespace_name

############################################

–1. 查看oracle最大连接数

sql>show parameter processes    #最大连接数

–2. 修改最大连接数

sql>alter system set processes=value scope=spfile

–重启数据库

sql>shutdown force

sql>start force

–3. 查看当前连接数

sql>select * from v$session where username is not null

–4. 查看不同用户的连接数

sql>select username,count(username) from v$session where username is not null group by username #查看指定用户的连接数

–5. 查看活动的连接数

sql>select count(*) from v$session where status='active' #查看并发连接数

–6. 查看指定程序的连接数

sql>select count(*) from v$session where program='jdbc thin client' #查看jdbc连接oracle的数目

–7. 查看数据库安装实例(dba权限)

sql>select * from v$instance

–8. 查看运行实例名

sql>show parameter instance_name

–9. 查看数据库名

sql>show parameter db_name

–10. 查看数据库域名

sql>show parameter db_domain

–11. 查看数据库服务名

sql>show parameter service_names

–12. 查看全局数据库名

sql>show parameter global

–13. 查看表空间使用率

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

-- (1) select dbf.tablespace_name,         dbf.totalspace "总量(m)" ,         dbf.totalblocks as "总块数" ,         dfs.freespace "剩余总量(m)" ,         dfs.freeblocks "剩余块数" ,         (dfs.freespace / dbf.totalspace) * 100 as "空闲比例"    from ( select t.tablespace_name,                 sum (t.bytes) / 1024 / 1024 totalspace,                 sum (t.blocks) totalblocks            from dba_data_files t           group by t.tablespace_name) dbf,         ( select tt.tablespace_name,                 sum (tt.bytes) / 1024 / 1024 freespace,                 sum (tt.blocks) freeblocks            from dba_free_space tt           group by tt.tablespace_name) dfs   where trim(dbf.tablespace_name) = trim(dfs.tablespace_name) -- (2) select t. name "tablespace name" ,         free_space,         (total_space - free_space) used_space,         total_space    from ( select tablespace_name, sum (bytes / 1024 / 1024) free_space            from sys.dba_free_space           group by tablespace_name) free ,         ( select b. name , sum (bytes / 1024 / 1024) total_space            from sys.v_$datafile a, sys.v_$tablespace b           where a.ts# = b.ts#           group by b. name ) t   where free .tablespace_name = t. name