Oracle 常用的查询操作

–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

–11. 查看oracle最大连接数
sql>show parameter processes    #最大连接数

–12. 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

–13. 查看当前连接数
sql>select * from v$session where username is not null

–14. 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

–15. 查看活动的连接数
sql>select count(*) from v$session where status='active' #查看并发连接数

–16. 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

–17. 查看数据库安装实例(dba权限)
sql>select * from v$instance

–18. 查看运行实例名
sql>show parameter instance_name

–19. 查看数据库名
sql>show parameter db_name

–20. 查看数据库域名
sql>show parameter db_domain

–21. 查看数据库服务名
sql>show parameter service_names

–22. 查看全局数据库名
sql>show parameter global

–23. 查看表空间使用率

-- (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