oracle¶ÔtopµÄÖ§³Ö
1.ÔÚORACLEÖÐʵÏÖSELECT TOP N
ÓÉÓÚORACLE²»Ö§³ÖSELECT TOPÓï¾ä£¬ËùÒÔÔÚORACLEÖо³£ÊÇÓÃORDER BY¸úROWNUMµÄ×éºÏÀ´ÊµÏÖSELECT TOP NµÄ²éѯ¡£
¼òµ¥µØËµ£¬ÊµÏÖ·½·¨ÈçÏÂËùʾ£º
SELECT¡¡ÁÐÃû£±£®£®£®ÁÐÃû£î¡¡from
(SELECT¡¡ÁÐÃû£±£®£®£®ÁÐÃû£î¡¡from ±íÃû ORDER BY ÁÐÃû£±£®£®£®ÁÐÃû£î)
WHERE ROWNUM <= N£¨³é³ö¼Ç¼Êý£©
ORDER BY ROWNUM ASC
ÏÂÃæ¾Ù¸öÀý×Ó¼òµ¥ËµÃ÷һϡ£
¹Ë¿Í±ícustomer(id,name)ÓÐÈçÏÂÊý¾Ý£º
ID NAME
01 first
02 Second
03 third
04 forth
05 fifth
06 sixth
07 seventh
08 eighth
09 ninth
10 tenth
11 last
Ôò°´NAMEµÄ×Öĸ˳³é³öǰÈý¸ö¹Ë¿ÍµÄSQLÓï¾äÈçÏÂËùʾ£º
SELECT * from
(SELECT * from CUSTOMER ORDER BY NAME)
WHERE ROWNUM <= 3
ORDER BY ROWNUM ASC
Êä³ö½á¹ûΪ£º
ID NAME
08 eighth
05 fifth
01 first
2.ÔÚTOP N¼Í¼Öгé³öµÚM£¨M <= N£©Ìõ¼Ç¼
Ôڵõ½ÁËTOP NµÄÊý¾ÝÖ®ºó£¬ÎªÁ˳é³öÕâNÌõ¼Ç¼ÖеĵÚMÌõ¼Ç¼£¬ÎÒÃÇ¿ÉÒÔ¿¼ÂÇ´ÓROWNUM×ÅÊÖ¡£ÎÒÃÇÖªµÀ£¬ROWNUMÊǼǼ±íÖÐÊý¾Ý±àºÅµÄÒ»¸öÒþ²Ø×ӶΣ¬ËùÒÔ¿ÉÒÔÔڵõ½TOP NÌõ¼Ç¼µÄʱºòͬʱ³é³ö¼Ç¼µÄROWNUM£¬È»ºóÔÙ´ÓÕâNÌõ¼Ç¼ÖгéÈ¡¼Ç¼±àºÅΪMµÄ¼Ç¼£¬¼´Ê¹ÎÒÃÇÏ£ÍûµÃµ½µÄ½á¹û¡£
´ÓÉÏÃæµÄ·ÖÎö¿ÉÒÔºÜÈÝÒ׵õ½ÏÂÃæµÄSQ
Ïà¹ØÎĵµ£º
oracleÁ¬½ÓÊý¾Ý¿â²âÊÔ´úÂë
/**
*
* ˵Ã÷£º
* £¨1£©±¾ÀýʹÓÃJDBC_ODBCÇŽøÐÐÊý¾Ý¿âÁ¬½Ó£¬¹Ê´ËÐèÒªODBCÊý¾ÝÔ´
* £¨2£©±¾ÀýÖÐSQLΪ¸üÐÂÓï¾ä£¬¹Ê´ËʹÓÃÔØÌåµÄexecuteUpdate·½·¨£¬²¢ÇÒ·µ»ØÊÜÓ°Ïì¼Ç¼Êý
* (3) ÅäÖÃÁ¬½ÓORACLEµÄodbcÊý¾ÝÔ´ora
*/ ......
Ŀǰ£¬ÕýÔò±í´ïʽÒѾÔںܶàÈí¼þÖеõ½¹ã·ºµÄÓ¦Ó㬰üÀ¨*nix£¨Linux, UnixµÈ£©£¬HPµÈ²Ù×÷ϵͳ£¬PHP£¬C#£¬JavaµÈ¿ª·¢»·¾³¡£
Oracle 10gÕýÔò±í´ïʽÌá¸ßÁËSQLÁé»îÐÔ¡£ÓÐЧµÄ½â¾öÁËÊý¾ÝÓÐЧÐÔ£¬ ÖØ¸´´ÊµÄ±æÈÏ, Î޹صĿհ׼ì²â£¬»òÕß·Ö½â¶à¸öÕýÔò×é³É
µÄ×Ö·û´®µÈÎÊÌâ¡£
Oracle 10gÖ§³ÖÕýÔò±í´ïʽµÄËĸöк¯Êý·Ö±ðÊÇ£ºREGEXP_L ......
oracle¿Í»§¶Ë Á¬½ÓPL/SQL
ÏÂÔØ¿Í»§¶Ëµ½Ä³¸ö·¾¶
ÐÞ¸ÄÅäÖÃÎļþ
D:\oracle\product\10.2.0\db_1\NETWORK\ADMIN\tnsnames.ora
# tnsnames.ora Network Configuration File: D:\oracle\product\10.2.0\db_1\network\admin\tnsnames.ora
# Generated by Oracle configuration tools.
SQLCLUB =
(DESCRIPTION ......
¾¡Á¿ÉÙÓÃIN²Ù×÷·û£¬»ù±¾ÉÏËùÓеÄIN²Ù×÷·û¶¼¿ÉÒÔÓÃEXISTS´úÌæ¡£
²»ÓÃNOT IN²Ù×÷·û£¬¿ÉÒÔÓÃNOT EXISTS»òÕßÍâÁ¬½Ó+Ìæ´ú¡£
OracleÔÚÖ´ÐÐIN×Ó²éѯʱ£¬Ê×ÏÈÖ´ÐÐ×Ó²éѯ£¬½«²éѯ½á¹û·ÅÈëÁÙʱ±íÔÙÖ´ÐÐÖ÷²éѯ¡£¶øEXISTÔòÊÇÊ×Ïȼì²éÖ÷²éѯ£¬È»ºóÔËÐÐ×Ó²éѯֱµ½ÕÒµ½µÚÒ»¸öÆ¥ÅäÏî¡£NOT EXISTS±ÈNOT INЧÂÊÉԸߡ£µ«¾ßÌåÔÚÑ¡ÔñIN»òEXIST² ......
OracleÖеÄHash JoinÏé½â
Ò»¡¢ hash join¸ÅÄî
Hashjoin(HJ)ÊÇÒ»ÖÖÓÃÓÚequi-join£¨¶øanti-join¾ÍÊÇʹÓÃNOT INʱµÄjoin£©µÄ¼¼Êõ¡£
ÔÚOracleÖУ¬ËüÊÇ´Ó7.3¿ªÊ¼ÒýÈëµÄ£¬ÒÔ´úÌæsort-mergeºÍnested-loop join·½Ê½£¬
Ìá¸ßЧÂÊ¡£ÔÚCBO£¨hash joinÖ»ÓÐÔÚCBO²Å¿ÉÄܱ»Ê¹Óõ½£©Ä£Ê½Ï£¬ÓÅ»¯Æ÷¼ÆËã´ú ......