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
Wait Problem Potential Fix Sequential Read Indicates many index reads—tune the code (especially joins) Scattered Read Indicates many full table scans—tune the code; cache small tables ......
Navicat for xxx ÊÇÒ»¸öÓÅÐãµÄÊý¾Ý¿â¹ÜÀí¿Í»§¶Ë£¬ÓÐ MySQL¡¢Oracle µÈ°æ±¾¡£½¨Òé´ó¼Ò×îºÃÓà Enterprise °æ±¾£¬¹¦ÄÜÈ«ÃæÒ»Ð©£¬µ«½ÏÖ®ÓÚÃâ·ÑµÄ Lite °æ£¬ÆóÒµ°æ¿ÉÊÇÒª»¨Òø×ÓÂòµÄ¡£
°²×° Navicat for Oracle ºó£¬Ê×ÏÈÐèÒª½¨Ò»¸ö“Á¬½Ó”£¬×÷Ϊij¸ö¹ÜÀíÈÎÎñµÄ±êʶ£¬ÒòΪ×÷Î ......
--´´½¨±í¿Õ¼ä
create tablespace Ãû³Æ
(
datafile='·¾¶\Ãû³Æ.ora',
size='50M',
autoextend='on'
)
/
--´´½¨ÁÙʱ±í¿Õ¼ä
create temporary tablespace Ãû³Æ
(
tempfile='·¾¶\Ãû³Æ.ora',
size='50M',
autoextend='on'
)
/
--´´½¨Óû§
create user Óû§Ãû idtenified by ÃÜÂë
/
--ΪÓû§Ö¸¶¨ ......
ORACLEµÄJOB´´½¨£¬¿ÉϧµÄÊDz»ÄܸÄÃû£¬Ö»ÄÜÊÇÊý×ÖµÄÃû×Ö¡£
DECLARE X NUMBER;
BEGIN
SYS.DBMS_JOB.SUBMIT
( job => X
,what => 'compile_invalid_object;'
,next_date => to_date('20-04-2010 ......
1£© Ñ¡Ôñ×îÓÐЧÂʵıíÃû˳Ðò(Ö»ÔÚ»ùÓÚ¹æÔòµÄÓÅ»¯Æ÷ÖÐÓÐЧ)£º
ORACLEµÄ½âÎöÆ÷°´ÕÕ´ÓÓÒµ½×óµÄ˳Ðò´¦Àífrom×Ó¾äÖеıíÃû£¬from×Ó¾äÖÐдÔÚ×îºóµÄ±í(»ù´¡±í driving table)½«±»×îÏÈ´¦Àí£¬ÔÚfrom×Ó¾äÖаüº¬¶à¸ö±íµÄÇé¿öÏÂ,Äã±ØÐëÑ¡Ôñ¼Ç¼ÌõÊý×îÉٵıí×÷Ϊ»ù´¡±í¡£Èç¹ûÓÐ3¸öÒÔÉϵıíÁ¬½Ó²éѯ, ÄǾÍÐèҪѡÔñ½»²æ±í(intersection ......