引自：
http://www.newebug.com/article/database/2167.shtml虛擬字段
133. CURRVAL 和 nextval
為表創建序列
CREATE SEQUENCE EMPSEQ ... ;
SELECT empseq.currval FROM DUAL ;
自動插入序列的數值
INSERT INTO emp
valueS (empseq.nextval, 'LEWIS', 'CLERK',
7902, SYSDATE, 1200, NULL, 20) ;
134. ROWNUM
按設定排序的行的序號
SELECT * FROM emp WHERE ROWNUM < 10 ;
135. ROWID
返回行的物理地址
SELECT ROWID, ename FROM emp WHERE deptno = 20 ;
136. 將N秒轉換為時分秒格式？
set serverout on
declare
N number := 1000000;
ret varchar2(100);
begin
ret := trunc(n/3600) || '小時' || to_char(to_date(mod(n,3600),'sssss'),'fmmi"分 "ss"秒"') ;
dbms_output.put_line(ret);
end;
137. 如何查詢做比較大的排序的進程？
SELECT b.tablespace, b.segfile#, b.segblk#, b.blocks, a.sid, a.serial#,
a.username, a.osuser, a.status
FROM v$session a,v$sort_usage b
WHERE a.saddr = b.session_addr
ORDER BY b.tablespace, b.segfile#, b.segblk#, b.blocks ;
138. 如何查詢做比較大的排序的進程的SQL語句？
select /*+ ORDERED */ sql_text from v$sqltext a
where a.hash_value = (
select sql_hash_value from v$session b
where b.sid = &sid and b.serial# = &serial)
order by piece asc ;
139. 如何查找重復記錄？
SELECT * FROM TABLE_NAME
WHERE ROWID!=(SELECT MAX(ROWID) FROM TABLE_NAME D
WHERE TABLE_NAME.COL1=D.COL1 AND TABLE_NAME.COL2=D.COL2);
140. 如何刪除重復記錄？
DELETE FROM TABLE_NAME
WHERE ROWID!=(SELECT MAX(ROWID) FROM TABLE_NAME D
WHERE TABLE_NAME.COL1=D.COL1 AND TABLE_NAME.COL2=D.COL2);
141. 如何快速編譯所有視圖？
SQL >SPOOL VIEW1.SQL
SQL >SELECT ‘ALTER VIEW ‘||TNAME||’
COMPILE;’ FROM TAB;
SQL >SPOOL OFF
然后執行VIEW1.SQL即可。
SQL >@VIEW1.SQL;
142. ORA-01555 SNAPSHOT TOO OLD的解決辦法
增加MINEXTENTS的值，增加區的大小，設置一個高的OPTIMAL值。
143. 事務要求的回滾段空間不夠，表現為表空間用滿（ORA-01560錯誤），回滾段擴展到達參數 MAXEXTENTS的值（ORA-01628）的解決辦法.
向回滾段表空間添加文件或使已有的文件變大；增加MAXEXTENTS的值。
144. 如何加密ORACLE的存儲過程？
下列存儲過程內容放在AA.SQL文件中
create or replace procedure testCCB(i in number) as
begin
dbms_output.put_line('輸入參數是'||to_char(i));
end;
SQL>wrap iname=a.sql;
PL/SQL Wrapper: Release 8.1.7.0.0 - Production on Tue Nov 27 22:26:48 2001
Copyright (c) Oracle Corporation 1993, 2000. All Rights Reserved.
Processing AA.sql to AA.plb
運行AA.plb
SQL> @AA.plb ;
145. 如何監控事例的等待？
select event,sum(decode(wait_Time,0,0,1)) "Prev",
sum(decode(wait_Time,0,1,0)) "Curr",count(*) "Tot"
from v$session_Wait
group by event order by 4;
146. 如何回滾段的爭用情況？
select name, waits, gets, waits/gets "Ratio"
from v$rollstat C, v$rollname D
where C.usn = D.usn;
147. 如何監控表空間的 I/O 比例？
select B.tablespace_name name,B.file_name "file",A.phyrds pyr,
A.phyblkrd pbr,A.phywrts pyw, A.phyblkwrt pbw
from v$filestat A, dba_data_files B
where A.file# = B.file_id
order by B.tablespace_name;
148. 如何監控文件系統的 I/O 比例？
select substr(C.file#,1,2) "#", substr(C.name,1,30) "Name",
C.status, C.bytes, D.phyrds, D.phywrts
from v$datafile C, v$filestat D
where C.file# = D.file#;
149. 如何在某個用戶下找所有的索引？
select user_indexes.table_name, user_indexes.index_name,uniqueness, column_name
from user_ind_columns, user_indexes
where user_ind_columns.index_name = user_indexes.index_name
and user_ind_columns.table_name = user_indexes.table_name
order by user_indexes.table_type, user_indexes.table_name,
user_indexes.index_name, column_position;
150. 如何監控 SGA 的命中率？
select a.value + b.value "logical_reads", c.value "phys_reads",
round(100 * ((a.value+b.value)-c.value) / (a.value+b.value)) "BUFFER HIT RATIO"
from v$sysstat a, v$sysstat b, v$sysstat c
where a.statistic# = 38 and b.statistic# = 39
and c.statistic# = 40;
151. 如何監控 SGA 中字典緩沖區的命中率？
select parameter, gets,Getmisses , getmisses/(gets+getmisses)*100 "miss ratio",
(1-(sum(getmisses)/ (sum(gets)+sum(getmisses))))*100 "Hit ratio"
from v$rowcache
where gets+getmisses <>0
group by parameter, gets, getmisses;
152. 如何監控 SGA 中共享緩存區的命中率，應該小于1% ？
select sum(pins) "Total Pins", sum(reloads) "Total Reloads",
sum(reloads)/sum(pins) *100 libcache
from v$librarycache;
select sum(pinhits-reloads)/sum(pins) "hit radio",sum(reloads)/sum(pins) "reload percent"
from v$librarycache;
153. 如何顯示所有數據庫對象的類別和大小？
select count(name) num_instances ,type ,sum(source_size) source_size ,
sum(parsed_size) parsed_size ,sum(code_size) code_size ,sum(error_size) error_size,
sum(source_size) +sum(parsed_size) +sum(code_size) +sum(error_size) size_required
from dba_object_size
group by type order by 2;
154. 監控 SGA 中重做日志緩存區的命中率，應該小于1%
SELECT name, gets, misses, immediate_gets, immediate_misses,
Decode(gets,0,0,misses/gets*100) ratio1,
Decode(immediate_gets+immediate_misses,0,0,
immediate_misses/(immediate_gets+immediate_misses)*100) ratio2
FROM v$latch WHERE name IN ('redo allocation', 'redo copy');
155. 監控內存和硬盤的排序比率，最好使它小于 .10，增加 sort_area_size
SELECT name, value FROM v$sysstat WHERE name IN ('sorts (memory)', 'sorts (disk)');
156. 如何監控當前數據庫誰在運行什么SQL語句？
SELECT osuser, username, sql_text from v$session a, v$sqltext b
where a.sql_address =b.address order by address, piece;
157. 如何監控字典緩沖區？
SELECT (SUM(PINS - RELOADS)) / SUM(PINS) "LIB CACHE" FROM V$LIBRARYCACHE;
SELECT (SUM(GETS - GETMISSES - USAGE - FIXED)) / SUM(GETS) "ROW CACHE" FROM V$ROWCACHE;
SELECT SUM(PINS) "EXECUTIONS", SUM(RELOADS) "CACHE MISSES WHILE EXECUTING" FROM V$LIBRARYCACHE;
后者除以前者,此比率小于1%,接近0%為好。
SELECT SUM(GETS) "DICTIONARY GETS",SUM(GETMISSES) "DICTIONARY CACHE GET MISSES"
FROM V$ROWCACHE
158. 監控 MTS
select busy/(busy+idle) "shared servers busy" from v$dispatcher;
此值大于0.5時，參數需加大
select sum(wait)/sum(totalq) "dispatcher waits" from v$queue where type='dispatcher';
select count(*) from v$dispatcher;
select servers_highwater from v$mts;
servers_highwater接近mts_max_servers時，參數需加大
159. 如何知道當前用戶的ID號?
SQL>SHOW USER;
OR
SQL>select user from dual;
160. 如何查看碎片程度高的表?
SELECT segment_name table_name , COUNT(*) extents
FROM dba_segments WHERE owner NOT IN ('SYS', 'SYSTEM') GROUP BY segment_name
HAVING COUNT(*) = (SELECT MAX( COUNT(*) ) FROM dba_segments GROUP BY segment_name);
162. 如何知道表在表空間中的存儲情況?
select segment_name,sum(bytes),count(*) ext_quan from dba_extents where
tablespace_name='&tablespace_name' and segment_type='TABLE' group by tablespace_name,segment_name;
163. 如何知道索引在表空間中的存儲情況?
select segment_name,count(*) from dba_extents where segment_type='INDEX' and owner='&owner'
group by segment_name;
164、如何知道使用CPU多的用戶session?
11是cpu used by this session
select a.sid,spid,status,substr(a.program,1,40) prog,a.terminal,osuser,value/60/100 value
from v$session a,v$process b,v$sesstat c
where c.statistic#=11 and c.sid=a.sid and a.paddr=b.addr order by value desc;
165. 如何知道監聽器日志文件?
以8I為例
$ORACLE_HOME/NETWORK/LOG/LISTENER.LOG
166. 如何知道監聽器參數文件?
以8I為例
$ORACLE_HOME/NETWORK/ADMIN/LISTENER.ORA
167. 如何知道TNS 連接文件?
以8I為例
$ORACLE_HOME/NETWORK/ADMIN/TNSNAMES.ORA
168. 如何知道Sql*Net 環境文件?
以8I為例
$ORACLE_HOME/NETWORK/ADMIN/SQLNET.ORA
169. 如何知道警告日志文件?
以8I為例
$ORACLE_HOME/ADMIN/SID/BDUMP/SIDALRT.LOG
170. 如何知道基本結構?
以8I為例
$ORACLE_HOME/RDBMS/ADMIN/STANDARD.SQL
171. 如何知道建立數據字典視圖?
以8I為例
$ORACLE_HOME/RDBMS/ADMIN/CATALOG.SQL
172. 如何知道建立審計用數據字典視圖?
以8I為例
$ORACLE_HOME/RDBMS/ADMIN/CATAUDIT.SQL
173. 如何知道建立快照用數據字典視圖?
以8I為例
$ORACLE_HOME/RDBMS/ADMIN/CATSNAP.SQL