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        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
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1. ½«Êý¾Ý¿âÍêÈ«µ¼³ö
    Óû§Ãûsystem ÃÜÂësystem µ¼³öµ½OracleÓû§Ä¿Â¼ÏµÄtestdb20100522.dmpÎļþÖÐ
    #exp system/system@testdb file=testdb20100522.dmp full=y
2. ½«Êý¾Ý¿âÖÐsystemÓû§ÓësysÓû§µÄ±íµ¼³ö
    #exp system/system@testdb file= testdb20100522.d ......

µãµãµÎµÎ(Oracle)

insert into
    select * into t_dest from t_src; -- ÒªÇóÄ¿±ê±í²»´æÔÚ
    insert into t_dest(a, b) select a, b from t_src; -- ÒªÇóÄ¿±ê±íÒÑ´æÔÚ
¶¯Ì¬SQL
    execute immediate ......

110¸öOracle ³£Óú¯ÊýµÄ×ܽá

SQLÖеĵ¥¼Ç¼º¯Êý
1.ASCII
·µ»ØÓëÖ¸¶¨µÄ×Ö·û¶ÔÓ¦µÄÊ®½øÖÆÊý;
SQL> select ascii(A) A,ascii(a) a,ascii(0) zero,ascii( ) space from dual;
A A ZERO SPACE
--------- --------- --------- ---------
65 97 48 32
2.CHR
¸ø³öÕûÊý,·µ»Ø¶ÔÓ¦µÄ×Ö·û;
SQL> select chr(54740) zhao,chr(65) chr65 from dual;
......

Oracle±í¿Õ¼ä³£ÓòÙ×÷

1. ²é¿´Oracle´´½¨¹ýÄÄЩÓû§
   >select username from all_users;
2. ²é¿´Oracle´´½¨¹ýÄÄЩ±í¿Õ¼ä£¬±í¿Õ¼äµÄÃû×ֺʹóС
   >select t.tablespace_name, round(sum(bytes/(1024*1024)),0) ts_size
    from dba_tablespaces t, dba_data_files d
    wher ......

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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