t_tudent(sid,sname,sage,ssex,sdept) 学生表

　　t_course(cid,cname,tid) 课程表

　　t_score( scid,sid,cid,grade) 成绩表

　　t_teacher(tid,tname) 教师表

　　问题：

　　1、查询“001”课程比“002”课程成绩高的所有学生的学号;

　　select t1.sid from

　　(select sid,grade from t_score where cid = '001') t1,

　　(select sid,grade from t_score where cid = '002') t2

　　where t1.grade >t2.grade and t1.sid = t2.sid;

　　select t2.sid,t2.ca,t2.cb(

　　select t1.sid,sum(t1.ca) ca,sum(t1.cb) cb

　　from

　　(

　　select sid,

　　CASE WHEN cid = '001' THEN grade ELSE 0 END ca,

　　CASE WHEN cid = '002' THEN grade ELSE 0 END cb

　　from t_score

　　)t1

　　GROUP BY sid

　　)t2

　　where t2.ca > t2.cb

　　2、查询平均成绩大于60分的同学的学号和平均成绩;

　　select sid,avg(grade ) from t_score

　　group by sid

　　having avg(grade ) >60;

　　3、查询所有同学的学号、姓名、选课数、总成绩;

　　select t1.sid,t1.sname,count(t2.cid),sum(grade ) from t_student t1

　　left join t_score t2

　　on t1.sid = t2sid

　　group by t1sid,t1.sname;

　　4、查询姓“李”的老师的个数;

　　select count(distinct(tname)) from t_teacher where tname like '李%';

　　5、查询没学过“叶平”老师课的同学的学号、姓名;

　　select sid, sname from t_student

　　where sid not in

　　(

　　select distinct(t1.sid) from t_score t1,t_course t2,t_teacher t3

　　where t1.cid = t2.cid and t3.tid = t2.tid and t3.tname = '叶平'

　　);

　　6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名;

　　select t0.sid,t0.sname from t_student t0, t_score t1

　　where t0.sid = t1.sid and t1.cid = '001'

　　and exists

　　(

　　select * from t_score t2 where t2.sid = t1.sid and t2.cid = '002'

　　);

　　7、查询学过“叶平”老师所教的所有课的同学的学号、姓名;

　　select sid,sname from t_student

　　where sid in

　　(

　　select sid from t_score t1 ,t_course t2,t_teacher t3

　　where t1.cid=t2.cid

　　and t3.tid=t2.tid

　　and t3.tname = '叶平'

　　group by sid

　　having count(t1.cid)=(

　　select count(cid) from t_course t1,t_teacher t2

　　where t2.tid=t1.tid and t2.tname = '叶平'

　　)

　　);

　　8、查询“001”课程比“002”课程成绩高的所有同学的学号、姓名;

　　Select sid,sname from

　　(

　　select t1.sid,t1.sname,t2.grade ,

　　(

　　select grade from t_score t3

　　where t3.sid = t1.sid and t3.cid = '002'

　　) grade2

　　from t_student t1, t_score t2

　　where t1sid = t2.sid and t2.cid = '001'

　　) S_2

　　where grade 2 < grade ;

　　9、查询所有课程成绩小于60分的同学的学号、姓名;

　　select sid,sname from t_student

　　where sid not in

　　(

　　select t1.sid from t_student t1, t_score t2

　　where t1.sid = t2.sid and t2.grade >60

　　);

　　10、查询没有学全所有课的同学的学号、姓名;

　　select t1.sid,t1.sname from Student t1, t_score t2

　　where t1.sid = t2.sid

　　group by t1.sid,t1.sname

　　having count(t2.cid) < (select count(cid) from t_course);

　　11、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名;

　　select sid,sname from t_student t1, t_score t2

　　where t1.sid = t2.sid

　　and cid in (select cid from t_score where sid = '1001');

　　12、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名;

　　select distinct t2.sid,t1.sname from t_student t1, t_score t2

　　where t1.sid = t2.sid

　　and cid in (select cid from t_score where sid = '001');

　　13、把“ t_score”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩;

　　update t_score t4 set grade =(select avg( t3.grade ) from t_score t3 where t3.cid= t4.cid )

　　from t_course t1,t_teacher t2

　　where t1.cid = t4.cid

　　and t1.tid = t2.tid

　　and t2.tname = '叶平');

　　14、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名;

　　select sid from t_score

　　where cid in (select cid from t_score where sid = '1002')

　　group by sid

　　having count(*)=(select count(*) from t_score where sid = '1002');

　　15、删除学习“叶平”老师课的 t_score表记录;

　　delect t_score from t_course t1 ,t_teacher t2

　　Where t1.cid = t2.cid

　　and t1.tid = t2.tid

　　and t2.tname = '叶平';

　　16、向 t_score表中插入一些记录，这些记录要求符合以下条件：没有上过编号“003”课程的同学学号、2、

　　号课的平均成绩;

　　insert t_score

　　select sid,'002',(Select avg(grade ) from t_score where cid = '002')

　　from t_student

　　where sid not in (Select sid from t_score where cid = '002');

　　17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生ID,,数据库,企业管理,英语,有效课程数,有效平均分

　　SELECT sid as 学生ID,

　　(SELECT grade FROM t_score WHERE sid=t.sid AND cid='004') AS 数据库,

　　(SELECT grade FROM t_score WHERE sid=t.sid AND cid='001') AS 企业管理,

　　(SELECT grade FROM t_score WHERE sid=t.sid AND cid='006') AS 英语,

　　COUNT(*) AS 有效课程数,

　　AVG(t.grade ) AS 平均成绩

　　FROM t_score AS t

　　GROUP BY sid

　　ORDER BY avg(t.grade )

　　18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分

　　SELECT t1.cid As 课程ID,t1.grade AS 最高分,t2.grade AS 最低分

　　FROM t_score t1 , t_score t2

　　WHERE t1.cid = t2.cid

　　and t1.grade = (

　　SELECT MAX(tt1.grade ) FROM t_score tt1,t_student tt2

　　WHERE t1.cid = tt1.cid and tt2.sid = tt1.sid

　　GROUP BY tt1.cid

　　)

　　AND t2.grade = (

　　SELECT MIN(tt3.grade ) FROM t_score AS tt3

　　WHERE t2.cid = tt3.cid GROUP BY tt2.cid

　　);

　　19、按各科平均成绩从低到高和及格率的百分数从高到低顺序

　　SELECT t.cid AS 课程号,max(course.cname)AS 课程名,isnull(AVG(grade ),0) AS 平均成绩 ,

　　100 * SUM(CASE WHEN isnull(grade ,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数

　　FROM t_score t1,t_course t2

　　where t1.cid = t2.cid

　　GROUP BY t1.cid

　　ORDER BY 100 * SUM(CASE WHEN isnull(grade ,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC

　　20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理(001)，马克思(002)，OO&UML (003)，数据库(004)

　　SELECT

　　SUM(

　　CASE WHEN cid = '001'

　　THEN grade ELSE 0 END)/SUM(CASE cid WHEN '001'

　　THEN 1 ELSE 0 END

　　) AS 企业管理平均分 ,

　　100 * SUM(

　　CASE WHEN cid = '001' AND grade >= 60

　　THEN 1 ELSE 0 END)/SUM(CASE WHEN cid = '001'

　　THEN 1 ELSE 0 END

　　) AS 企业管理及格百分数 FROM t_score

　　21、查询不同老师所教不同课程平均分从高到低显示

　　SELECT max(t3.tid) AS 教师ID,MAX(t3.tname) AS 教师姓名,

　　T2.cid AS 课程ID,MAX(t2.cname) AS 课程名称,AVG(grade ) AS 平均成绩

　　FROM t_score AS t1,t_course AS t2 ,t_teacher AS t3

　　where t1.cid = t2.cid and t2.tid = t3.tid

　　GROUP BY t2.cid

　　ORDER BY AVG(grade ) DESC ;