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Oracle sql ÐÔÄÜÓÅ»¯µ÷Õû    1. Ñ¡ÓÃÊʺϵÄORACLEÓÅ»¯Æ÷
        ORACLEµÄÓÅ»¯Æ÷¹²ÓÐ3ÖÖ£º
a. RULE £¨»ùÓÚ¹æÔò£©  
b. COST £¨»ùÓڳɱ¾£©
c. CHOOSE £¨Ñ¡ÔñÐÔ£©
    ÉèÖÃȱʡµÄÓÅ»¯Æ÷£¬¿ÉÒÔͨ¹ý¶Ôinit.oraÎļþÖÐOPTIMIZER_MODE²ÎÊýµÄ¸÷ÖÖÉùÃ÷£¬ÈçRULE£¬COST£¬CHOOSE£¬ALL_ROWS£¬FIRST_ROWS . Ä㵱ȻҲÔÚSQL¾ä¼¶»òÊǻỰ£¨session£©¼¶¶ÔÆä½øÐи²¸Ç¡£
    ΪÁËʹÓûùÓڳɱ¾µÄÓÅ»¯Æ÷£¨CBO£¬ Cost-Based Optimizer£© £¬ Äã±ØÐë¾­³£ÔËÐÐanalyze ÃüÁÒÔÔö¼ÓÊý¾Ý¿âÖеĶÔÏóͳ¼ÆÐÅÏ¢£¨object statistics£©µÄ׼ȷÐÔ¡£
    Èç¹ûÊý¾Ý¿âµÄÓÅ»¯Æ÷ģʽÉèÖÃΪѡÔñÐÔ£¨CHOOSE£©£¬ÄÇôʵ¼ÊµÄÓÅ»¯Æ÷ģʽ½«ºÍÊÇ·ñÔËÐйýanalyzeÃüÁîÓйء£ Èç¹ûtableÒѾ­±»analyze¹ý£¬ ÓÅ»¯Æ÷ģʽ½«×Ô¶¯³ÉΪCBO £¬ ·´Ö®£¬Êý¾Ý¿â½«²ÉÓÃRULEÐÎʽµÄÓÅ»¯Æ÷¡£
    ÔÚȱʡÇé¿öÏ£¬ORACLE²ÉÓÃCHOOSEÓÅ»¯Æ÷£¬ÎªÁ˱ÜÃâÄÇЩ²»±ØÒªµÄÈ«±íɨÃ裨full table scan£© £¬ Äã±ØÐ뾡Á¿±ÜÃâʹÓÃCHOOSEÓÅ»¯Æ÷£¬¶øÖ±½Ó²ÉÓûùÓÚ¹æÔò»òÕß»ùÓڳɱ¾µÄÓÅ»¯Æ÷¡£
    2.       ·ÃÎÊTableµÄ·½Ê½ORACLE ²ÉÓÃÁ½ÖÖ·ÃÎʱíÖмǼµÄ·½Ê½£º
    a.       È«±íɨÃè
        È«±íɨÃè¾ÍÊÇ˳ÐòµØ·ÃÎʱíÖÐÿÌõ¼Ç¼¡£ ORACLE²ÉÓÃÒ»´Î¶ÁÈë¶à¸öÊý¾Ý¿é£¨database block£©µÄ·½Ê½ÓÅ»¯È«±íɨÃè¡£
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    ΪÁ˲»Öظ´½âÎöÏàͬµÄSQLÓï¾ä£¬ÔÚµÚÒ»´Î½âÎöÖ®ºó£¬ ORACLE½«SQLÓï¾ä´æ·ÅÔÚÄÚ´æÖС£Õâ¿éλÓÚϵͳȫ¾ÖÇøÓòSGA£¨system global area£©µÄ¹²Ïí³Ø£¨shared buffer pool£©ÖеÄÄÚ´æ¿ÉÒÔ±»ËùÓеÄÊý¾Ý¿âÓû§¹²Ïí¡£ Òò´


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Oracle 10g R2 RACÔÚVMWAREÉϵݲװ

½¨Á¢sshÐÅÈΣ¬racµÄ°²×°ÒªÓÃsshºÍscpÀ´¿½±´°²×°Îļþ¡£
ÔÚËùÓеĽڵãÉÏÔËÐУº
mkdir ~/.ssh
chmod 700 ~/.ssh
ssh-keygen -t rsa
ssh-keygen -t dsa
ÔÚrdb1½ÚµãÉÏÖ´ÐУº
ssh rdb1 cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
ssh rdb1 cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys
ssh rdb2 ......

Oracle trunc º¯ÊýµÄʹÓÃ

OracleµÄtrunc º¯ÊýÒ»°ãÓÃÀ´ ¶ÔÈÕÆÚºÍʱ¼ä½øÐнØÈ¡¡£
 
1¡¢Êý×Ö´¦Àí ¡£½ØÈ¡
 
 select trunc(5.75),trunc(5.75,1),trunc(5.75,-1),trunc(556.234,-2) from dual;
 
 
Êä³ö:
TRUNC(5.75) TRUNC(5.75,1) TRUNC(5.75,-1) TRUNC(556.234,-2)
----------- ------------- -------------- ----- ......

oracle¼¶ÁªÉ¾³ý

oracleÖÐʹÓÃon delete cascadeºÍon delete set nullÀ´½¨Á¢Íâ¼ü
ÆäÃæÎÒÃǽéÉÜÁË´´½¨Íâ¼üÔ¼ÊøʱÈç¹ûʹÓÃoracleĬÈϵĴ´½¨·½Ê½£¬ÔÚɾ³ý±»²ÎÕÕµÄÊý¾Ýʱ£¬½«ÎÞ·¨±»É¾³ý£¬ÕâÒ»µãÔÚoracle9iÖиøÁËÎÒÃǸü¶àÁé»îµÄÑ¡Ôñ£¬ÎÒÃÇ¿ÉÊÇʹÓÃon delete cascadeºÍ on delete set null¹Ø¼ü×ÖÀ´¾ö¶¨É¾³ý±»²ÎÕÕÊý¾ÝʱÊÇ·ñÒª½«²ÎÕÕÕâ¸öÊý¾ÝµÄÄÇÐ ......

oracle splitº¯Êý

CREATE OR REPLACE TYPE ty_str_array IS TABLE OF VARCHAR2 (4000);
CREATE OR REPLACE FUNCTION fn_split (p_str IN VARCHAR2, p_delimiter IN VARCHAR2)
    RETURN ty_str_split
IS
    j INT := 0;
    i INT := 1;
    len INT := 0;
 &nbs ......
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