实验答案(四-五-六)参考答案

实验四 简单查询和连接查询1. 简单查询实验用Transact-SQL语句表示下列操作，在“学生选课“数据库中实现其数据查询操作：(1) 查询数学系学生的学号和姓名。select sno,snamefrom studentwhere dept=数学系;(2) 查询选修了课程的学生学号。 select distinct(sno)from sc;(3) 查询选修课程号为0101的学生学号和成绩，并要求对查询结果按成绩降序排列，如果成绩相同则按学号升序排列。select distinct(sno),gradefrom scwhere cno=0101order by grade desc,sno asc;(4) 查询选修课程号为0101的成绩在80-90 分之间的学生学号和成绩，并将成绩乘以系数0.8 输出。select distinct(sno),grade*0.8 as sorefrom scwhere cno=0101 and grade between 80 and 90;(5) 查询数学系或计算机系姓张的学生的信息。 select *from studentwhere dept in (数学系,计算机系)and sname like 张% ;(6) 查询缺少了成绩的学生的学号和课程号。 select sno,cnofrom scwhere grade is null;2. 连接查询实验用Transact-SQL语句表示，并在“学生选课”数据库中实现下列数据连接查询操作：(1) 查询每个学生的情况以及他（她）所选修的课程。 select student.*,amefrom student,sc,coursewhere student.sno=sc.sno and o=o; (2) 查询学生的学号、姓名、选修的课程名及成绩。 select student.sno,sname,cname,gradefrom student,sc,coursewhere student.sno=sc.sno and o=o;(3) 查询选修离散数学 课程且成绩为90 分以上的学生学号、姓名及成绩。select student.sno,sname,gradefrom student,sc,coursewhere student.sno=sc.sno and o=o and cname=离散数学 and grade=90;(4) 查询每一门课的间接先行课（即先行课的先行课）。select o,second.pcnofrom course as first,course as secondwhere first.pcno=o;实验五 嵌套查询用TransacTransact-SQL语句表示，在学生选课库中实现其数据嵌套查询操作：(l) 查询选修了离散数学的学生学号和姓名。select sno,sname from student where sno in (select sno from sc where cno= (select cno from course where cname=离散数学);(2) 查询0101课程的成绩高于张林的学生学号和成绩。select sno,gradefrom scwhere cno=0101 and grade(select grade from sc where cno=0101 and sno=(select sno From student Where sname=张林);(3) 查询其他系中年龄小于计算机系年龄最大者的学生。select * from student where dept计算机系 and age(select max(age) from student where dept=计算机系);(4) 查询其他系中比计算机系学生年龄都小的学生。(3)中的max换成min即可。(5) 查询同牟万里数据库原理课程分数相同的学生的学号。 select sno from sc where grade=(select grade from student,sc,course where student.sno=sc.sno and o=o and ame=数据库原理 and sname=牟万里);(6) 查询选修了0206 课程的学生姓名。select sname from student where sno in (select sno from sc where cno=0206);(7) 查询没有选修0206 课程的学生姓名。在(5)的in前加not即可。(8) 查询选修了全部课程的学生的姓名。SELECT SNAMEFROM STUDENT WHERE SNO IN ( SELECT SNO FROM SC GROUP BY SNO HAVING COUNT(*)= ( SELECT COUNT(*) FROM COURSE);select snamefrom studentwhere not exists (select * from course where not exists (select * from sc where sno=student.sno and cno=o);(9) 查询与学号为“09001103”的学生所选修的全部课程相同的学生学号和姓名。select sno,sname From student Where sno09001103 and not exists( select * From sc as x Where sno=09001103 and not exists (select * From sc as y Where y.sno=student.sno and o=o ) ; (10) 查询至少选修了学号为“09001103”的学生所选修的全部课程的学生学号和姓名。select sno,snamefrom studentwhere sno in(select scx.sno from sc scx where not exists(select * from sc scy where scy.sno=09001103 and not exists(select * from sc scz where scz.sno=scx.sno and o=o);实验六 组合查询和统计查询在学生选课数据库中实现其查询操作：(1) 查找选修“计算机基础”课程的学生成绩比此课程的平均成绩大的学生学号，成绩。select x.sno,x.grade From sc as x Where x.grade( select avg(y.grade) From sc as y,course as c Where ame=计算机基础) and o= (select cno From course Where cname=计算机基础);(2) 查询选修计算机基础课程的学生的平均成绩。select avg(grade) From sc Where sno in (select sno From sc Where cno= (select cno From course Where cname=计算机基础);(3) 查询年龄大于女同学平均年龄的男同学姓名和年龄。select sname,age From student Where sex=男 and age(select avg(age) From student Where sex=女);(4) 列出各系学生的总人数，并按人数进行降序排列。select dept ,count(*) as total From student Group by dept order by total desc;(5) 统计各系各门课程的平均成绩。select dept ,cno,avg(grade) From student,sc Group by dept,cno(6) 查询选修计算机基础和离散数学的学生学号和平均成绩。select s1.sno,avg(grade) as 平均分 From sc as s1 Where 计算机基础 in (select cna