Ò׽ؽØÍ¼Èí¼þ¡¢µ¥Îļþ¡¢Ãâ°²×°¡¢´¿ÂÌÉ«¡¢½ö160KB

ÈçºÎ¿´¶®ORACLEÖ´Ðмƻ®

ÈçºÎ¿´¶®ORACLEÖ´Ðмƻ®
Ò»¡¢Ê²Ã´ÊÇÖ´Ðмƻ®
An explain plan is a representation of the access path that is taken when a query is executed within Oracle.
¶þ¡¢ÈçºÎ·ÃÎÊÊý¾Ý
At the physical level Oracle reads blocks of data. The smallest amount of data read is a single Oracle block, the largest is constrained by operating system limits (and multiblock i/o). Logically Oracle finds the data to read by using the following methods:
Full Table Scan (FTS)    --È«±íɨÃè
Index Lookup (unique & non-unique)    --Ë÷ÒýɨÃ裨ΨһºÍ·ÇΨһ£©
Rowid    --ÎïÀíÐÐid
Èý¡¢Ö´Ðмƻ®²ã´Î¹ØÏµ
When looking at a plan, the rightmost (ie most inndented) uppermost operation is the first thing that is executed. --²ÉÓÃ×îÓÒ×îÉÏ×îÏÈÖ´ÐеÄÔ­Ôò¿´²ã´Î¹ØÏµ£¬ÔÚͬһ¼¶Èç¹ûij¸ö¶¯×÷ûÓÐ×ÓID¾Í×îÏÈÖ´ÐÐ
1.Ò»¸ö¼òµ¥µÄÀý×Ó£º
SQL> select  /*+parallel (e 4)*/  *  from  emp  e;
Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=1 Card=82 Bytes=7134)
   1    0   TABLE ACCESS* (FULL) OF 'EMP' (Cost=1 Card=82 Bytes=7134):Q5000
--[:Q5000]±íʾÊDz¢Ðз½Ê½
   1 PARALLEL_TO_SERIAL            SELECT /*+ NO_EXPAND ROWID(A1) */ A1."EMPNO"
                                   ,A1."ENAME",A1."JOB",A1."MGR",A1."HI
ÓÅ»¯Ä£Ê½ÊÇCHOOSEµÄÇé¿öÏ£¬¿´Cost²ÎÊýÊÇ·ñÓÐÖµÀ´¾ö¶¨²ÉÓÃCBO»¹ÊÇRBO£º
SELECT STATEMENT [CHOOSE] Cost=1234 --CostÓÐÖµ£¬²ÉÓÃCBO
SELECT STATEMENT [CHOOSE]           --CostΪ¿Õ£¬²ÉÓÃRBO(9IÊÇÈç´ËÏÔʾµÄ)
2.²ã´ÎµÄ¸¸×Ó¹ØÏµµÄÀý×Ó£º
PARENT1
**FIRST CHILD
****FIRST GRANDCHILD
**SECOND CHILD
Here the same principles apply


Ïà¹ØÎĵµ£º

Oracle ·ÖÇø±í


Oracle ·ÖÇø±í
OracleÌṩÁË·ÖÇø¼¼ÊõÒÔÖ§³ÖVLDB(Very Large DataBase)¡£·ÖÇø±íͨ¹ý¶Ô·ÖÇøÁеÄÅжϣ¬°Ñ·ÖÇøÁв»Í¬µÄ¼Ç¼£¬·Åµ½²»Í¬µÄ·ÖÇøÖС£·ÖÇøÍêÈ«¶ÔÓ¦ÓÃ͸Ã÷¡£ 
OracleµÄ·ÖÇø±í¿ÉÒÔ°üÀ¨¶à¸ö·ÖÇø£¬Ã¿¸ö·ÖÇø¶¼ÊÇÒ»¸ö¶ÀÁ¢µÄ¶Î£¨SEGMENT£©£¬¿ÉÒÔ´æ·Åµ½²»Í¬µÄ±í¿Õ¼äÖС£²éѯʱ¿ÉÒÔͨ¹ý²éѯ±íÀ´·ÃÎʸ÷¸ö·ÖÇøÖеÄÊý¾Ý£ ......

Oracle DB Link´´½¨

ÓÐʱºò£¬ÐèÒªÔÚÁ½¸öOracleÊý¾Ý¿âÖ®¼äÊÖ¹¤Í¬²½Êý¾Ýʱ£¬DBLinkÊÇ×î·½±ã¿ì½ÝµÄÊÖ¶ÎÖ®Ò»£¬´´½¨DBLinkµÄ·½Ê½Ò»°ãÊÇÕâÑù£º
create public database link <DBLinkÃû³Æ> connect to <±»Á¬½Ó¿âµÄÓû§Ãû> identified by <±»Á¬½Ó¿âµÄÃÜÂë> using '< ......

OracleÖÐÁÙʱ±í²úÉú¹ýÁ¿RedoµÄ˵Ã÷

OracleÖÐÁÙʱ±í²úÉú¹ýÁ¿RedoµÄ˵Ã÷
×î½ü,ÔÚOracle9iÖÐÄãÓùýÁÙʱ±íÂð?
ËüÊÇ·ñ¸øÄã´øÀ´ÁËÐÔÄÜÌá¸ß?Äã×¢Òâ¹ýô?
--------------------------------------------------------------------------------
ºÃÁËÑÔ¹éÕý´«.
ÎÒÃÇÖªµÀÁÙʱ±íÔÚDML²Ù×÷ÖпÉÒÔ¼õÉÙredoµÄÉú³É,´Ó¶øÔÚ±£´æÖмä½á¹û¼¯Ê±¿ÉÒÔ´øÀ´½Ï´óµÄÐÔÄÜÌá¸ß.
¿ÉÊÇ,È ......

oracle ¼ì²é±»ËøµÄ±í¼°½âËø

´¦Àí·½·¨Ò» £º
¼ì²éÄǸö±í±»Ëø
select sess.sid,sess.serial#, lo.oracle_username,lo.os_user_name,ao.object_name,lo.locked_mode
from v$locked_object lo,dba_objects ao,v$session sess
where ao.object_id = lo.object_id
and lo.session_id = sess.sid;
½âËø
alter system kill session '273,45';
´¦Àí·½·¨¶ ......

oracle²éѯÁ·Ï°

empÔ±¹¤±í
(empnoÔ±¹¤ºÅ/enameÔ±¹¤ÐÕÃû/job¹¤×÷/mgrÉϼ¶±àºÅ/hiredateÊܹÍÈÕÆÚ/salн½ð/commÓ¶½ð/deptno²¿ÃűàºÅ)
------1.Ñ¡Ôñ²¿ÃÅ30ÖеÄËùÓÐÔ±¹¤.
select ename
from emp
where deptno = 30;
------2.ÁгöËùÓаìÊÂÔ±(CLERK)µÄÐÕÃû£¬±àºÅºÍ²¿ÃűàºÅ.
select ename,empno,deptno
from emp
where job='CLERK';
--- ......
© 2009 ej38.com All Rights Reserved. ¹ØÓÚE½¡ÍøÁªÏµÎÒÃÇ | Õ¾µãµØÍ¼ | ¸ÓICP±¸09004571ºÅ