原帖連結:http://bbs.csdn.net/topics/280002741

建表語句：

CREATE TABLE student 
( 
     s_id    INT,
     sname varchar(32),
     sage  INT, 
     ssex  varchar(8) 
 );

CREATE TABLE course 
  ( 
     c_id    INT, 
     cname varchar(32), 
     t_id    INT 
  );

CREATE TABLE sc 
( 
     s_id  INT, 
     c_id  INT, 
     score INT 
) ;

CREATE TABLE teacher 
( 
     t_id    INT, 
     tname varchar(16) 
);

 

插入測試資料

insert into Student select 1,N'劉一',18,N'男' union all
 select 2,N'錢二',19,N'女' union all
 select 3,N'張三',17,N'男' union all
 select 4,N'李四',18,N'女' union all
 select 5,N'王五',17,N'男' union all
 select 6,N'趙六',19,N'女' ;
 
 insert into Teacher select 1,N'葉平' union all
 select 2,N'賀高' union all
 select 3,N'楊豔' union all
 select 4,N'周磊';
 
 insert into Course select 1,N'語文',1 union all
 select 2,N'數學',2 union all
 select 3,N'英語',3 union all
 select 4,N'物理',4;
 
 insert into SC 
 select 1,1,56 union all 
 select 1,2,78 union all 
 select 1,3,67 union all 
 select 1,4,58 union all 
 select 2,1,79 union all 
 select 2,2,81 union all 
 select 2,3,92 union all 
 select 2,4,68 union all 
 select 3,1,91 union all 
 select 3,2,47 union all 
 select 3,3,88 union all 
 select 3,4,56 union all 
 select 4,2,88 union all 
 select 4,3,90 union all 
 select 4,4,93 union all 
 select 5,1,46 union all 
 select 5,3,78 union all 
 select 5,4,53 union all 
 select 6,1,35 union all 
 select 6,2,68 union all 
 select 6,4,71;
 

常見問題

1、查詢“001”課程比“002”課程成績高的所有學生的學號； 
	 select a.s_id FROM
	 (select s_id,score from sc where c_id = '001')a,(select s_id,score from sc where c_id = '002')b
	 where a.score > b.score and a.s_id = b.s_id;

2、查詢平均成績大於60分的同學的學號和平均成績； 
    select s_id,avg(score)
	  from sc
    group by s_id
    having avg(score)>60;
3、查詢所有同學的學號、姓名、選課數、總成績； 
   select Student.s_id,Student.Sname,count(SC.c_id),sum(score) 
   from Student left Outer join SC on Student.S_id=SC.S_id 
   group by Student.S_id,Sname ;
4、查詢姓“李”的老師的個數； 
		select DISTINCT(count(tname))
		from teacher
		where tname like '李%';
5、查詢沒學過“葉平”老師課的同學的學號、姓名； 
   select Student.S_id,Student.Sname 
   from Student  where s_id not in
   (select distinct( SC.S_id) from SC,Course,Teacher where  SC.C_id=Course.C_id and Teacher.T_id=Course.T_id and teacher.tname = '葉平')
   
    
6、查詢學過“001”並且也學過編號“002”課程的同學的學號、姓名； 
	
	select student.s_id,student.sname from SC,student where  SC.s_id=student.s_id and SC.C_id='001'
  and EXISTS 
  (select * from SC as SC2  where  SC2.s_id=SC.s_id and SC2.C_id='002')

7、查詢學過“葉平”老師所教的所有課的同學的學號、姓名；
   select s_id,sname
   from student
   where s_id in
   (select SC.S_id from SC,Course,Teacher where  SC.C_id=Course.C_id and Teacher.T_id=Course.T_id and teacher.tname = '葉平' 
   GROUP BY sc.s_id
   having count(SC.c_id) =
   (select count(c.c_id) from course c,teacher t
   where c.t_id=t.t_id and t.tname = '葉平')) ;
	
  
8、查詢課程編號“002”的成績比課程編號“001”課程低的所有同學的學號、姓名； 
     select a.s_id,a.sname from
  	(select sc.s_id,sc.score,student.sname from SC,student where  SC.s_id=student.s_id and SC.C_id='001')a,
  	(select sc.s_id,sc.score from SC,student where  SC.s_id=student.s_id and SC.C_id='002')b
    where a.s_id = b.s_id and a.score> b.score;


9、查詢所有課程成績小於60分的同學的學號、姓名； 
  select S_id,Sname 
  from Student 
  where S_id not in (select S.S_id from Student AS S,SC where S.S_id=SC.S_id and score>60); 

10、查詢沒有學全所有課的同學的學號、姓名； 
  select s.s_id,s.sname
  from student s,sc sc
  where s.s_id = sc.s_id
  GROUP BY s.s_id,s.sname
  HAVING COUNT(sc.c_id) < (select count(c_id) from course)
    
11、查詢至少有一門課與學號為“1”的同學所學相同的同學的學號和姓名； 
	 select  DISTINCT Student.s_id,Student.sname 
   from Student,sc where student.s_id = sc.s_id
	 and sc.c_id in (select c_id from sc where s_id='1')