1、查看表空间的名称及大小
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、查看表空间物理文件的名称及大小
select tablespace_name, file_id, file_name,
round(bytes/(1024*1024),0) total_space
from dba_data_files
order by tablespace_name;
3、查看回滚段名称及大小
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、查看表空间的使用情况
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、查看数据库库对象
select owner, object_type, status, count(*) count# from all_objects group by owner, object_type, status;
8、查看数据库的版本
Select version FROM Product_component_version
Where SUBSTR(PRODUCT,1,6)='Oracle';
9、查看数据库的创建日期和归档方式
Select Created, Log_Mode, Log_Mode From V＄Database;
10、捕捉运行很久的SQL
column username format a12
column opname format a16
column progress format a8
select username,sid,opname,
round(sofar*100 / totalwork,0) || '%' as progress,
time_remaining,sql_text
from v＄session_longops , v＄sql
where time_remaining <> 0
and sql_address = address
and sql_hash_value = hash_value
/
11、查看数据表的参数信息
SELECT partition_name, high_value, high_value_length, tablespace_name,
pct_free, pct_used, ini_trans, max_trans, initial_extent,
next_extent, min_extent, max_extent, pct_increase, FREELISTS,
freelist_groups, LOGGING, BUFFER_POOL, num_rows, blocks,
empty_blocks, avg_space, chain_cnt, avg_row_len, sample_size,
last_analyzed
FROM dba_tab_partitions
--WHERE table_name = :tname AND table_owner = :towner
ORDER BY partition_position
12、查看还没提交的事务
select * from v＄locked_object;
select * from v＄transaction;
13、查找object为哪些进程所用
select
p.spid,
s.sid,
s.serial# serial_num,
s.username user_name,
a.type object_type,
s.osuser os_user_name,
a.owner,
a.object object_name,
decode(sign(48 - command),
1,
to_char(command), 'Action Code #' || to_char(command)  action,
p.program oracle_process,
s.terminal terminal,
s.program program,
s.status session_status
from v＄session s, v＄access a, v＄process p
where s.paddr = p.addr and
s.type = 'USER' and
a.sid = s.sid and
a.object='SUBSCRIBER_ATTR'
order by s.username, s.osuser
14、回滚段查看
select rownum, sys.dba_rollback_segs.segment_name Name, v＄rollstat.extents
Extents, v＄rollstat.rssize Size_in_Bytes, v＄rollstat.xacts XActs,
v＄rollstat.gets Gets, v＄rollstat.waits Waits, v＄rollstat.writes Writes,
sys.dba_rollback_segs.status status from v＄rollstat, sys.dba_rollback_segs,
v＄rollname where v＄rollname.name(+) = sys.dba_rollback_segs.segment_name and
v＄rollstat.usn (+) = v＄rollname.usn order by rownum
15、耗资源的进程（top session）
select s.schemaname schema_name, decode(sign(48 - command), 1,
to_char(command), 'Action Code #' || to_char(command) action, status
session_status, s.osuser os_user_name, s.sid, p.spid , s.serial# serial_num,
nvl(s.username, '[Oracle process]') user_name, s.terminal terminal,
s.program program, st.value criteria_value from v＄sesstat st, v＄session s , v＄process p
where st.sid = s.sid and st.statistic# = to_number('38') and ('ALL' = 'ALL'
or s.status = 'ALL') and p.addr = s.paddr order by st.value desc, p.spid asc, s.username asc, s.osuser asc
16、查看锁（lock）情况
select /*+ RULE */ ls.osuser os_user_name, ls.username user_name,
decode(ls.type, 'RW', 'Row wait enqueue lock', 'TM', 'DML enqueue lock', 'TX',
'Transaction enqueue lock', 'UL', 'User supplied lock') lock_type,
o.object_name object, decode(ls.lmode, 1, null, 2, 'Row Share', 3,
'Row Exclusive', 4, 'Share', 5, 'Share Row Exclusive', 6, 'Exclusive', null)
lock_mode, o.owner, ls.sid, ls.serial# serial_num, ls.id1, ls.id2
from sys.dba_objects o, ( select s.osuser, s.username, l.type,
l.lmode, s.sid, s.serial#, l.id1, l.id2 from v＄session s,
v＄lock l where s.sid = l.sid ls where o.object_id = ls.id1 and o.owner
<> 'SYS' order by o.owner, o.object_name
17、查看等待（wait）情况
SELECT v＄waitstat.class, v＄waitstat.count count, SUM(v＄sysstat.value) sum_value
FROM v＄waitstat, v＄sysstat WHERE v＄sysstat.name IN ('db block gets',
'consistent gets') group by v＄waitstat.class, v＄waitstat.count
18、查看sga情况
SELECT NAME, BYTES FROM SYS.V_＄SGASTAT ORDER BY NAME ASC
19、查看catched object
SELECT owner, name, db_link, namespace,
type, sharable_mem, loads, executions,
locks, pins, kept FROM v＄db_object_cache
20、查看V＄SQLAREA
SELECT SQL_TEXT, SHARABLE_MEM, PERSISTENT_MEM, RUNTIME_MEM, SORTS,
VERSION_COUNT, LOADED_VERSIONS, OPEN_VERSIONS, USERS_OPENING, EXECUTIONS,
USERS_EXECUTING, LOADS, FIRST_LOAD_TIME, INVALIDATIONS, PARSE_CALLS, DISK_READS,
BUFFER_GETS, ROWS_PROCESSED FROM V＄SQLAREA
21、查看object分类数量
select decode (o.type#,1,'INDEX' , 2,'TABLE' , 3 , 'CLUSTER' , 4, 'VIEW' , 5 ,
'SYNONYM' , 6 , 'SEQUENCE' , 'OTHER' object_type , count(*) quantity from
sys.obj＄ o where o.type# > 1 group by decode (o.type#,1,'INDEX' , 2,'TABLE' , 3
, 'CLUSTER' , 4, 'VIEW' , 5 , 'SYNONYM' , 6 , 'SEQUENCE' , 'OTHER' union select
'COLUMN' , count(*) from sys.col＄ union select 'DB LINK' , count(*) from
22、按用户查看object种类
select u.name schema, sum(decode(o.type#, 1, 1, NULL)) indexes,
sum(decode(o.type#, 2, 1, NULL)) tables, sum(decode(o.type#, 3, 1, NULL))
clusters, sum(decode(o.type#, 4, 1, NULL)) views, sum(decode(o.type#, 5, 1,
NULL)) synonyms, sum(decode(o.type#, 6, 1, NULL)) sequences,
sum(decode(o.type#, 1, NULL, 2, NULL, 3, NULL, 4, NULL, 5, NULL, 6, NULL, 1))
others from sys.obj＄ o, sys.user＄ u where o.type# >= 1 and u.user# =
o.owner# and u.name <> 'PUBLIC' group by u.name order by
sys.link＄ union select 'CONSTRAINT' , count(*) from sys.con＄
23、有关connection的相关信息
1）查看有哪些用户连接
select s.osuser os_user_name, decode(sign(48 - command), 1, to_char(command),
'Action Code #' || to_char(command) action, p.program oracle_process,
status session_status, s.terminal terminal, s.program program,
s.username user_name, s.fixed_table_sequence activity_meter, ' query,
0 memory, 0 max_memory, 0 cpu_usage, s.sid, s.serial# serial_num
from v＄session s, v＄process p where s.paddr=p.addr and s.type = 'USER'
order by s.username, s.osuser
2）根据v.sid查看对应连接的资源占用等情况
select n.name,
v.value,
n.class,
n.statistic#
from v＄statname n,
v＄sesstat v
where v.sid = 71 and
v.statistic# = n.statistic#
order by n.class, n.statistic#
3）根据sid查看对应连接正在运行的sql
select /*+ PUSH_SUBQ */
command_type,
sql_text,
sharable_mem,
persistent_mem,
runtime_mem,
sorts,
version_count,
loaded_versions,
open_versions,
users_opening,
executions,
users_executing,
loads,
first_load_time,
invalidations,
parse_calls,
disk_reads,
buffer_gets,
rows_processed,
sysdate start_time,
sysdate finish_time,
'>' || address sql_address,
'N' status
from v＄sqlarea
where address = (select sql_address from v＄session where sid = 71)
24、查询表空间使用情况select a.tablespace_name "表空间名称",
100-round((nvl(b.bytes_free,0)/a.bytes_alloc)*100,2) "占用率(%)",
round(a.bytes_alloc/1024/1024,2) "容量(M)",
round(nvl(b.bytes_free,0)/1024/1024,2) "空闲(M)",
round((a.bytes_alloc-nvl(b.bytes_free,0))/1024/1024,2) "使用(M)",
Largest "最大扩展段(M)",
to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') "采样时间"
from (select f.tablespace_name,
sum(f.bytes) bytes_alloc,
sum(decode(f.autoextensible,'YES',f.maxbytes,'NO',f.bytes)) maxbytes
from dba_data_files f
group by tablespace_name) a,
(select f.tablespace_name,
sum(f.bytes) bytes_free
from dba_free_space f
group by tablespace_name) b,
(select round(max(ff.length)*16/1024,2) Largest,
ts.name tablespace_name
from sys.fet＄ ff, sys.file＄ tf,sys.ts＄ ts
where ts.ts#=ff.ts# and ff.file#=tf.relfile# and ts.ts#=tf.ts#
group by ts.name, tf.blocks) c
where a.tablespace_name = b.tablespace_name and a.tablespace_name = c.tablespace_name
25、 查询表空间的碎片程度
select tablespace_name,count(tablespace_name) from dba_free_space group by tablespace_name
having count(tablespace_name)>10;
alter tablespace name coalesce;
alter table name deallocate unused;
create or replace view ts_blocks_v as
select tablespace_name,block_id,bytes,blocks,'free space' segment_name from dba_free_space
union all
select tablespace_name,block_id,bytes,blocks,segment_name from dba_extents;
select * from ts_blocks_v;
select tablespace_name,sum(bytes),max(bytes),count(block_id) from dba_free_space
group by tablespace_name;
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2005-9-14  关于ORACLE中Decode和Sign的用法[转]
一、根据具体条件值进行判断，并返回相应的值：
decode(p1,v01,v02,v11,v12....)
如果p1=v01,结果为v02；如果p1=v11,则为v12....；否则为p1,类推
相当于多个case...when语句
sign正弦
sign(角度)
如 sign(30)
--------------------------------------------------------------------------------
decode(x,v1,s1,v2,s2...)
if x=v1 then s1 else if x=v2 then s2...
sign(x)
x=0,sign(x)=0;
x>0,sign(x)=1;
x<0,sign(x)=-1;
--------------------------------------------------------------------------------
关于sign的用法yxxx(小孬) 的才是正确的。
--------------------------------------------------------------------------------
个人认为：
decode(x,v1,s1,v2,s2...)
if x=v1 then s1 else if x=v2 then s2...
(如果p1=v01,结果为v02；如果p1=v11,则为v12....；否则为p1,类推)
和sql server中的
select mycolumn=
case columnA
when value1 then result1
...
else other result
from tableA where ....
二、含义解释：
decode(条件,值1,翻译值1,值2,翻译值2,...值n,翻译值n,缺省值)
该函数的含义如下：
IF 条件=值1 THEN
RETURN(翻译值1)
ELSIF 条件=值2 THEN
RETURN(翻译值2)
......
ELSIF 条件=值n THEN
RETURN(翻译值n)
ELSE
RETURN(缺省值)
END IF
· 使用方法：
1、比较大小
select decode(sign(变量1-变量2),-1,变量1,变量2) from dual; --取较小值
sign()函数根据某个值是0、正数还是负数，分别返回0、1、-1
例如：
变量1=10，变量2=20
则sign(变量1-变量2)返回-1，decode解码结果为“变量1”，达到了取较小值的目的。
2、表、视图结构转化
现有一个商品销售表sale，表结构为：
month char(6) --月份
sell number(10,2) --月销售金额
现有数据为：
200001 1000
200002 1100
200003 1200
200004 1300
200005 1400
200006 1500
200007 1600
200101 1100
200202 1200
200301 1300
想要转化为以下结构的数据：
year char(4) --年份
month1 number(10,2) --1月销售金额
month2 number(10,2) --2月销售金额
month3 number(10,2) --3月销售金额
month4 number(10,2) --4月销售金额
month5 number(10,2) --5月销售金额
month6 number(10,2) --6月销售金额
month7 number(10,2) --7月销售金额
month8 number(10,2) --8月销售金额
month9 number(10,2) --9月销售金额
month10 number(10,2) --10月销售金额
month11 number(10,2) --11月销售金额
month12 number(10,2) --12月销售金额
结构转化的SQL语句为：
create or replace view
v_sale(year,month1,month2,month3,month4,month5,month6,month7,month8,month9,month10,month11,month12)
as
select
substrb(month,1,4),
sum(decode(substrb(month,5,2),'01',sell,0)),
sum(decode(substrb(month,5,2),'02',sell,0)),
sum(decode(substrb(month,5,2),'03',sell,0)),
sum(decode(substrb(month,5,2),'04',sell,0)),
sum(decode(substrb(month,5,2),'05',sell,0)),
sum(decode(substrb(month,5,2),'06',sell,0)),
sum(decode(substrb(month,5,2),'07',sell,0)),
sum(decode(substrb(month,5,2),'08',sell,0)),
sum(decode(substrb(month,5,2),'09',sell,0)),
sum(decode(substrb(month,5,2),'10',sell,0)),
sum(decode(substrb(month,5,2),'11',sell,0)),
sum(decode(substrb(month,5,2),'12',sell,0))
from sale
group by substrb(month,1,4);
1<a<3 then 10 ===> decode(sign(a-1)*sign(a-3),-1,10)
1<a<=3 then 10 ===> decode(sign(a-1)+sign(a-3),0,10,1,10)
1<=a<=3 then 10 ===> decode(sign(a-1)*sign(a-3),0,10,-1,10)
参考一下：
decode ( sign (a-1) , 1, decode(sign(a-3), 1, 2, 1 , 0)
SQL> select decode ( sign (0-1) , 1, decode(sign(0-3), 1, 2, 1 , 0) from dual;
DECODE(SIGN(0-1),1,DECODE(SIGN
------------------------------
0
SQL> select decode ( sign (2-1) , 1, decode(sign(2-3), 1, 2, 1 , 0) from dual;
DECODE(SIGN(2-1),1,DECODE(SIGN
------------------------------
1
SQL> select decode ( sign (4-1) , 1, decode(sign(4-3), 1, 2, 1 , 0) from dual;
DECODE(SIGN(4-1),1,DECODE(SIGN
------------------------------
2
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