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Student(S#,Sname,Sage,S***) ѧÉú±í
Course(C#,Cname,T#) ¿Î³Ì±í
SC(S#,C#,score) ³É¼¨±í
Teacher(T#,Tname) ½Ìʦ±í
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1¡¢²éѯ“001”¿Î³Ì±È“002”¿Î³Ì³É¼¨¸ßµÄËùÓÐѧÉúµÄѧºÅ£»
  select a.S# from (select s#,score from SC where C#='001') a,(select s#,score
  from SC where C#='002') b
  where a.score>b.score and a.s#=b.s#;
2¡¢²éѯƽ¾ù³É¼¨´óÓÚ60·ÖµÄͬѧµÄѧºÅºÍƽ¾ù³É¼¨£»
    select S#,avg(score)
    from sc
    group by S# having avg(score) >60;
3¡¢²éѯËùÓÐͬѧµÄѧºÅ¡¢ÐÕÃû¡¢Ñ¡¿ÎÊý¡¢×ܳɼ¨£»
  select Student.S#,Student.Sname,count(SC.C#),sum(score)
  from Student left Outer join SC on Student.S#=SC.S#
  group by Student.S#,Sname
4¡¢²éѯÐÕ“ÀÄÀÏʦµÄ¸öÊý£»
  select count(distinct(Tname))
  from Teacher
  where Tname like 'Àî%';
5¡¢²éѯûѧ¹ý“Ҷƽ”ÀÏʦ¿ÎµÄͬѧµÄѧºÅ¡¢ÐÕÃû£»
    select Student.S#,Student.Sname
    from Student  
    where S# not in (select distinct( SC.S#) from SC,Course,Teacher where  SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='Ҷƽ');
6¡¢²éѯѧ¹ý“001”²¢ÇÒҲѧ¹ý±àºÅ“002”¿Î³ÌµÄͬѧµÄѧºÅ¡¢ÐÕÃû£»
  select Student.S#,Student.Sname from Student,SC where Student.S#=SC.S# and SC.C#='001'and exists( Select * from SC as SC_2 where SC_2.S#=SC.S# and SC_2.C#='002');
7¡¢²éѯѧ¹ý“Ҷƽ”ÀÏʦËù½ÌµÄËùÓпεÄͬѧµÄѧºÅ¡¢ÐÕÃû£»
  select S#,Sname
  from Student
  where S# in (select S# from SC ,Course ,Teacher where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='Ҷƽ' group by S# having count(SC.C#)=(select count(C#) from Course,Teacher  where Teacher.T#=Course.T# and Tname='Ҷƽ'));
8¡¢²éѯ¿Î³Ì±àºÅ“002”µÄ³É¼¨±È¿Î³Ì±àºÅ“001”¿