SQL
	
    
    
	ÌâÄ¿1:
ÎÊÌâÃèÊö:
 S (SNO,SNAME) ѧÉú¹ØÏµ¡£SNO ΪѧºÅ£¬SNAME ΪÐÕÃû
 C (CNO,CNAME,CTEACHER) ¿Î³Ì¹ØÏµ¡£CNO Ϊ¿Î³ÌºÅ£¬CNAME Ϊ¿Î³ÌÃû£¬CTEACHER ΪÈονÌʦ
 SC(SNO,CNO,SCGRADE) Ñ¡¿Î¹ØÏµ¡£SCGRADE Ϊ³É¼¨
 1.£¨1£©ÕÒ³öÑ¡ÐÞ¹ý“ÀîÃ÷”ÀÏʦ½²Êڿγ̵ÄËùÓÐѧÉúÐÕÃû
 --ʵÏÖ´úÂë:·¨Ò»
Select *
from SC,C,S
Where SC.CNO=C.CNO AND SC.SNO=S.SNO AND CTEACHER='ÀîÃ÷'
---·¨¶þ£º-------------
Select *
from S 
Where Sno IN( Select Sno 
              from C,SC 
              Where C.[Cno]=SC.[Cno] AND CTEACHER='ÀîÃ÷')
 
£¨2£©ÕÒ³öûÓÐÑ¡ÐÞ¹ý“ÀîÃ÷”ÀÏʦ½²Êڿγ̵ÄËùÓÐѧÉúÐÕÃû
 --ʵÏÖ´úÂë:·¨Ò»
Select SName 
from S 
Where [Sno] NOT IN( Select SC.[Sno]
                    from SC,C
                    Where SC.CNO=C.CNO AND CTEACHER='ÀîÃ÷')
 
£¨3£©ÕÒ³öûÓÐÑ¡ÐÞ¹ý¿Î³ÌºÅΪ"1"µÄËùÓÐѧÉúÐÕÃû
 --ʵÏÖ´úÂë
Select SName 
from S 
Where [Sno] NOT IN( Select [Sno] from SC Where CNO='1')
 
------------------------------------------------------------------------------------------------------------------------------------------ 
 2. ÁгöÓжþÃÅÒÔÉÏ(º¬Á½ÃÅ)²»¼°¸ñ¿Î³ÌµÄѧÉúÐÕÃû¼°Æäƽ¾ù³É¼¨
 --ʵÏÖ´úÂë:
Select S.SNO,S.SNAME,AVG_SCGRADE=AVG(SC.SCGRADE) 
from S,SC,( Select SNO 
                     from SC 
                     Where SCGRADE<60 
                     GROUP BY SNO 
  &nb
    
     
	
	
    
    
	Ïà¹ØÎĵµ£º
        
    
     ORACLEPL/SQL»ù´¡--ÓαêµÄѧϰÀ´Ô´£º
    Óαê×ÖÃæÀí½â¾ÍÊÇÓζ¯µÄ¹â±ê¡£ 
    ÓÃÊý¾Ý¿âÓïÑÔÀ´ÃèÊö£ºÓαêÊÇÓ³ÉäÔÚ½á¹û¼¯ÖÐÒ»ÐÐÊý¾ÝÉϵÄλÖÃʵÌ壬ÓÐÁËÓαêÓû§¾Í¿ÉÒÔ·ÃÎʽá¹û¼¯ÖеÄÈÎÒâÒ»ÐÐÊý¾ÝÁË£¬½«Óαê·ÅÖõ½Ä³Ðк󣬼´¿É¶Ô¸ÃÐÐÊý¾Ý½øÐвÙ×÷£¬ÀýÈçÌáÈ¡µ±Ç°ÐеÄÊý¾ÝµÈµÈ¡£ 
  ......
	
    
        
    
    1. Èç¹ûÄãÏ£ÍûʹÓÃselcet topÓï¾ä£¬²¢ÇÒ»¹Òª¸½´øwhereÌõ¼þ£¬ÄÇôÌõ¼þÖеÄÁо͵ÃÊǺÏÊʵÄË÷Òý£¬Èç¾Û¼¯Ë÷Òý¡¢¸´ºÏË÷ÒýÀïµÄÖ÷ÁÐ
 µÈ£¬Í¬Ê±£¬whereÌõ¼þÀïÒ²Òª¾¡Á¿±Ü¿ªÊ¹Óú¯Êý£¬or£¬ÅжÏNULLµÈ»áÒýÆðÈ«²¿É¨ÃèµÄÓï¾ä£¬²»È»Ö´ÐеÄÊÇÈ«±íɨÃè¡£
2. ͨ¹ýÉèÖÃSTATISTICSÎÒÃÇ¿ÉÒԲ鿴ִÐÐSQLʱµÄÖ´ÐÐЧÂÊÒÔ¼°Ïà¹ØÐÔÄܲâÊÔ ......
	
    
        
    
     (1)char¡¢varchar¡¢textºÍnchar¡¢nvarchar¡¢ntext
charºÍvarcharµÄ³¤¶È¶¼ÔÚ1µ½8000Ö®¼ä£¬ËüÃǵÄÇø±ðÔÚÓÚcharÊǶ¨³¤×Ö·ûÊý¾Ý£¬¶øvarcharÊDZ䳤×Ö·ûÊý¾Ý¡£Ëùν¶¨³¤¾ÍÊdz¤¶È¹Ì¶¨ µÄ£¬µ±ÊäÈëµÄÊý¾Ý³¤¶ÈûÓдﵽָ¶¨µÄ³¤¶Èʱ½«×Ô¶¯ÒÔÓ¢ÎĿոñÔÚÆäºóÃæÌî³ä£¬Ê¹³¤¶È´ïµ½ÏàÓ¦µÄ³¤¶È£»¶ø±ä³¤×Ö·ûÊý¾ÝÔò²»»áÒÔ¿Õ¸ñÌî³ä¡£ text´ ......
	
    
        
    
     2.¸ù¾ÝOracle Êý¾Ý¿âscott ģʽϵÄemp ±íºÍdept ±í£¬Íê³ÉÏÂÁвÙ×÷£º
      (1) ²éѯ20ºÅ²¿ÃŵÄËùÓÐÔ±¹¤ÐÅÏ¢£»
      (2) ²éѯËùÓй¤ÖÖΪCLERK µÄÔ±¹¤µÄÔ±¹¤ºÅ¡¢Ô±¹¤ÃûºÍ²¿Ãźţ»
      (3) ²éѯ½±½ðCOMM ¸ßÓÚ¹¤×ÊSAL µÄÔ±¹¤ÐÅÏ¢£»
  ......