一、表关系
请创建如下表，并创建相关约束
班级表：class 学生表：student
cid caption grade_id sid sname gender class_id
1 一年一班 1 1 乔丹 女 1
2 二年一班 2 2 艾弗森 女 1
3 三年二班 3 3 科比 男 2
老师表：teacher 课程表：course
tid tname cid cname teacher_id
1 张三 1 生物 1
2 李四 2 体育 1
3 王五 3 物理 2
成绩表：score 年级表：class_grade
sid student_id course_id score gid gname
1 1 1 60 1 一年级
2 1 2 59 2 二年级
3 2 2 99 3 三年级
班级任职表：teach2cls
tcid tid cid
1 1 1
2 1 2
3 2 1
4 3 2
二、操作表
# 题目：
1、自行创建测试数据；
2、查询学生总人数；
3、查询“生物”课程和“物理”课程成绩都及格的学生id和姓名；
4、查询每个年级的班级数，取出班级数最多的前三个年级；
5、查询平均成绩最高和最低的学生的id和姓名以及平均成绩；
6、查询每个年级的学生人数；
7、查询每位学生的学号，姓名，选课数，平均成绩；
8、查询学生编号为“2”的学生的姓名、该学生成绩最高的课程名、成绩最低的课程名及分数；
9、查询姓“李”的老师的个数和所带班级数；
10、查询班级数小于5的年级id和年级名；
11、查询班级信息，包括班级id、班级名称、年级、年级级别(12为低年级，34为中年级，56为高年级)，示例结果如下；
班级id 班级名称 年级 年级级别
1 一年一班 一年级 低
12、查询学过“张三”老师2门课以上的同学的学号、姓名；
13、查询教授课程超过2门的老师的id和姓名；
14、查询学过编号“1”课程和编号“2”课程的同学的学号、姓名；
15、查询没有带过高年级的老师id和姓名；
16、查询学过“张三”老师所教的所有课的同学的学号、姓名；
17、查询带过超过2个班级的老师的id和姓名；
18、查询课程编号“2”的成绩比课程编号“1”课程低的所有同学的学号、姓名；
19、查询所带班级数最多的老师id和姓名；
20、查询有课程成绩小于60分的同学的学号、姓名；
21、查询没有学全所有课的同学的学号、姓名；
22、查询至少有一门课与学号为“1”的同学所学相同的同学的学号和姓名；
23、查询至少学过学号为“1”同学所选课程中任意一门课的其他同学学号和姓名；
24、查询和“2”号同学学习的课程完全相同的其他同学的学号和姓名；
25、删除学习“张三”老师课的score表记录；
26、向score表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“2”课程的同学学号；②插入“2”号课程的平均成绩；
27、按平均成绩从低到高显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
28、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；
29、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；
30、课程平均分从高到低显示（显示任课老师）；
31、查询各科成绩前三名的记录(不考虑成绩并列情况)
32、查询每门课程被选修的学生数；
33、查询选修了2门以上课程的全部学生的学号和姓名；
34、查询男生、女生的人数，按倒序排列；
35、查询姓“张”的学生名单；
36、查询同名同姓学生名单，并统计同名人数；
37、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；
38、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
39、查询课程编号为“3”且课程成绩在80分以上的学生的学号和姓名；
40、求选修了课程的学生人数
41、查询选修“王五”老师所授课程的学生中，成绩最高和最低的学生姓名及其成绩；
42、查询各个课程及相应的选修人数；
43、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；
44、查询每门课程成绩最好的前两名学生id和姓名；
45、检索至少选修两门课程的学生学号；
46、查询没有学生选修的课程的课程号和课程名；
47、查询没带过任何班级的老师id和姓名；
48、查询有两门以上课程超过80分的学生id及其平均成绩；
49、检索“3”课程分数小于60，按分数降序排列的同学学号；
50、删除编号为“2”的同学的“1”课程的成绩；
51、查询同时选修了物理课和生物课的学生id和姓名；
建表
create table class_grade( gid int primary key auto_increment, gname varchar(16) not null unique ); create table class( cid int primary key auto_increment, caption varchar(16) not null, grade_id int not null, foreign key(grade_id) references class_grade(gid) ); create table student( sid int primary key auto_increment, sname varchar(16) not null, gender enum('女','男') not null default '女', class_id int not null, foreign key(class_id) references class(cid) ); create table teacher( tid int primary key auto_increment, tname varchar(16) not null ); create table course( cid int primary key auto_increment, cname varchar(16) not null, teacher_id int not null, foreign key(teacher_id) references teacher(tid) ); create table score( sid int not null unique auto_increment, student_id int not null, course_id int not null, score int not null, primary key(student_id,course_id), foreign key(student_id) references student(sid) on delete cascade on update cascade, foreign key(course_id) references course(cid) on delete cascade on update cascade ); create table teach2cls( tcid int not null unique auto_increment, tid int not null, cid int not null, primary key(tid,cid), foreign key(tid) references teacher(tid) on delete cascade on update cascade, foreign key(cid) references class(cid) on delete cascade on update cascade );
准备数据
insert into class_grade(gname) values # 4个年级 ('一年级'), ('二年级'), ('三年级'), ('四年级'); insert into class(caption,grade_id) values # 9个班级 ('一年一班',1), ('一年二班',1), ('一年三班',1), ('二年一班',2), ('二年二班',2), ('三年一班',3), ('三年二班',3), ('四年一班',4), ('四年二班',4); insert into student(sname,gender,class_id) values # 12个学生 ('乔丹','女',1), ('艾弗森','女',1), ('科比','男',2), ('alice','女',2), ('alex','男',3), ('egon','男',4), ('lily','女',5), ('lucy','女',6), ('json','男',6), ('哈妹','女',7), ('霍建华','男',8), ('林心如','女',9); insert into teacher(tname) values # 4个老师 ('张三'), ('李四'), ('王五'), ('赵六'); insert into course(cname,teacher_id) values # 9个课程 ('生物',1), ('体育',1), ('物理',2), ('化学',3), ('美术',4), ('音乐',2), ('语文',3), ('数学',4), ('地理',2); insert into score(student_id,course_id,score) values # 12个学生，9个课程 (1,1,60), (1,2,59), (1,3,58), (1,4,22), (1,5,59), (1,6,60), (1,7,99), (1,8,100), (1,9,88), (2,1,99), (2,2,99), (2,3,89), (2,4,60), (2,5,59), (2,6,33), (2,7,56), (2,8,59), (2,9,60), (3,1,59), (3,3,30), (3,5,28), (3,7,70), (3,9,60), (4,2,59), (4,4,100), (4,6,90), (4,8,80), (5,1,59), (5,2,33), (5,3,12), (5,4,88), (6,5,100), (6,6,60), (6,7,59), (6,8,100), (7,9,20), (7,1,36), (7,3,57), (7,5,60), (8,2,61), (8,4,59), (8,6,62), (9,8,59), (9,1,60), (9,2,61), (9,3,21), (10,5,68), (10,9,99), (11,1,89), (11,7,99), (12,3,100), (12,8,60); insert into teach2cls(tid,cid) values # 4个老师 9个班级 (1,1), (1,2), (1,3), (1,5), (2,4), (2,6), (2,8), (2,9), (2,1), (2,5), (3,7), (3,1), (3,3), (3,5), (3,9), (4,7), (4,2), (4,4), (4,6), (4,8), (4,1);
补充数据
insert into score(student_id,course_id,score) values # 12个学生，9个课程 (6,1,60), (6,3,99), (10,1,70), (10,3,88); insert into student(sname,gender,class_id) values # 12个学生 ('alice_1','女',1), ('alice_2','女',2); insert into teacher(tname) values # 4个老师 ('李杰'); insert into class(caption,grade_id) values # 9个班级 ('一年四班',1), ('一年五班',1); insert into class_grade(gname) values # 4个年级 ('五年级'); insert into class(caption,grade_id) values # 9个班级 ('五年一班',5); insert into course(cname,teacher_id) values # 9个课程 ('研究',1); insert into teach2cls(tid,cid) values # 4个老师 9个班级 (1,12), (2,12); insert into score(student_id,course_id,score) values # 12个学生，9个课程 (1,2,60), (2,2,59); insert into student(sname,gender,class_id) values # 12个学生 ('张一','女',1), ('张二','男',2); insert into student(sname,gender,class_id) values # 12个学生 ('张一','女',3), ('张二','男',4); insert into score(student_id,course_id,score) values # 12个学生，9个课程 (7,8,60), (7,10,60), (4,10,88), (6,9,88); insert into score(student_id,course_id,score) values # 12个学生，9个课程 (2,1,60); insert into score(student_id,course_id,score) values # 12个学生，9个课程 (1,1,60), (2,1,70), (3,1,80);
http://www.cnblogs.com/wupeiqi/articles/5748496.html
答案：
#1、自行创建测试数据； 见table_data.txt #2、查询学生总人数； select count(sid) as count_student from student; #3、查询“生物”课程和“物理”课程成绩都及格的学生id和姓名； select sid, sname from student where sid in ( select score.student_id from score inner join course on score.course_id = course.cid where course.cname in ( '生物', '物理' ) and score.score >= 60 group by score.student_id having count(course_id) = 2 ); #4、查询每个年级的班级数，取出班级数最多的前三个年级； select # 没有包含班级数相同得排名前三 class_grade.gname from class_grade inner join ( select grade_id, count(cid) as count_cid from class group by grade_id order by count_cid desc limit 3 ) as t1 on class_grade.gid = t1.grade_id; select # 包含了班级数相同得排名前三 gname from class_grade where gid in ( select grade_id from class group by grade_id having count(cid) in ( select # 子查询in()里面不能包含limit; This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery' t1.count_cid from ( select distinct count(cid) as count_cid from class group by grade_id order by count_cid desc limit 3 ) as t1 ) ); #5、查询平均成绩最高和最低的学生的id和姓名以及平均成绩； select # 包含了平均成绩相等得情况下，多个学生 student.sid, student.sname, t1.avg_score from student inner join ( select student_id, avg(score) as avg_score from score group by student_id having avg(score) in ( ( select avg(score) as max_avg_score from score group by student_id order by avg(score) desc limit 1 ), ( select avg(score) as min_avg_score from score group by student_id order by avg(score) asc limit 1 ) ) ) as t1 on student.sid = t1.student_id; #6、查询每个年级的学生人数； select t1.grade_id, count(t1.sid) as count_student from ( select student.sid, class.grade_id from student, class where student.class_id = class.cid ) as t1 group by t1.grade_id; #7、查询每位学生的学号，姓名，选课数，平均成绩； select # 包含了没有选课得学生left join student.sid, student.sname, t1.count_course, t1.avg_score from student left join ( select student_id, count(course_id) as count_course, avg(score) as avg_score from score group by student_id ) as t1 on student.sid = t1.student_id; #8、查询学生编号为“2”的学生的姓名、该学生成绩最高的课程名、成绩最低的课程名及分数； select # 包含了成绩最高，最低相等得情况 student.sname, course.cname, t1.score from ( select student_id, course_id, score from score where student_id = 2 and score in ( ( select max(score) from score where student_id = 2 ), ( select min(score) from score where student_id = 2 ) ) ) as t1 inner join student on t1.student_id = student.sid inner join course on t1.course_id = course.cid; #9、查询姓“李”的老师的个数和所带班级数； select # 包含了姓"李"的老师没有带班级 teacher.tid, teacher.tname, t1.count_cid from teacher left join ( select tid, count(cid) as count_cid from teach2cls where tid in ( select tid from teacher where tname like '李%' ) group by tid ) as t1 on teacher.tid = t1.tid where teacher.tname like '李%'; #10、查询班级数小于5的年级id和年级名； select gid, gname from class_grade where gid in ( select grade_id from class group by grade_id having count(caption) < 5 ); #11、查询班级信息，包括班级id、班级名称、年级、年级级别(12为低年级，34为中年级，56为高年级)，示例结果如下； 班级id 班级名称 年级 年级级别 1 一年一班 一年级 低 select class.cid, class.caption, class_grade.gname, case when class_grade.gid between 1 and 2 then '低' when class_grade.gid between 3 and 4 then '中' when class_grade.gid between 5 and 6 then '高' else 0 end as '年级级别' from class, class_grade where class.grade_id = class_grade.gid; #12、查询学过“张三”老师2门课以上的同学的学号、姓名； select sid, sname from student where sid in ( select student_id from score where course_id in ( select course.cid from teacher, course where teacher.tid = course.teacher_id and teacher.tname = '张三' ) group by student_id having count(course_id) > 2 ); #13、查询教授课程超过2门的老师的id和姓名； select tid, tname from teacher where tid in ( select teacher_id from course group by teacher_id having count(cid) > 2 ); #14、查询学过编号“1”课程和编号“2”课程的同学的学号、姓名； select sid, sname from student where sid in ( select distinct student_id from score where course_id in ( 1, 2 ) ); #15、查询没有带过高年级的老师id和姓名； select tid, tname from teacher where tid not in ( select tid from teach2cls where cid in ( select t1.cid from ( select class.cid, class.caption, class_grade.gname, case when class_grade.gid between 1 and 2 then '低' when class_grade.gid between 3 and 4 then '中' when class_grade.gid between 5 and 6 then '高' else 0 end as grade_layer from class, class_grade where class.grade_id = class_grade.gid ) as t1 where t1.grade_layer = '高' ) ); # 另一种方法： select tid, tname from teacher where tid not in ( select tid from teach2cls where cid in ( select cid from class where grade_id in ( 5, 6 ) ) ); #16、查询学过“张三”老师所教的所有课的同学的学号、姓名； select sid, sname from student where sid in ( select student_id from score where course_id in ( select cid from course inner join teacher on teacher.tid = course.teacher_id where teacher.tname = '张三' ) ); #17、查询带过超过2个班级的老师的id和姓名； select tid, tname from teacher where tid in ( select tid from teach2cls group by tid having count(cid) > 2 ); #18、查询课程编号“2”的成绩比课程编号“1”课程低的所有同学的学号、姓名； select sid, sname from student where sid in ( select t1.student_id from ( select student_id, score from score where course_id = 2 group by student_id ) as t1, ( select student_id, score from score where course_id = 1 group by student_id ) as t2 where t1.student_id = t2.student_id and t1.score < t2.score ); #19、查询所带班级数最多的老师id和姓名； select # 包含了班级数最多相等的情况 tid, tname from teacher where tid in ( select tid from teach2cls group by tid having count(cid) = ( select count(cid) from teach2cls group by tid order by count(cid) desc limit 1 ) ); #20、查询有课程成绩小于60分的同学的学号、姓名； select sid, sname from student where sid in ( select distinct student_id from score where score < 60 ); #21、查询没有学全所有课的同学的学号、姓名； select sid, sname from student where sid not in ( select student_id from score group by student_id having count(course_id) = ( select count(cid) from course ) ); #22、查询至少有一门课与学号为“1”的同学所学相同的同学的学号和姓名； select # 包含了学号为1的同学 sid, sname from student where sid in ( select student_id from score where course_id in ( select course_id from score where student_id = 1 ) group by student_id ); #23、查询至少学过学号为“1”同学所选课程中任意一门课的其他同学学号和姓名； select # 没有包含学号为1的同学 sid, sname from student where sid in ( select student_id from score where course_id in ( select course_id from score where student_id = 1 ) group by student_id ) and sid != 1; #24、查询和“2”号同学学习的课程完全相同的其他同学的学号和姓名； select sid, sname from student where sid in ( select score.student_id from score, ( select course_id from score where student_id = 2 ) as t1 where score.course_id = t1.course_id and score.student_id != 2 group by score.student_id having count(score.course_id) = ( select count(course_id) from score where student_id = 2 ) ); #25、删除学习“张三”老师课的score表记录； delete from score where course_id in ( select course.cid from course, teacher where course.teacher_id = teacher.tid and teacher.tname = '张三' ) #26、向score表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“2”课程的同学学号；②插入“2”号课程的平均成绩； insert into score(student_id,course_id,score) select t1.sid, 2, t2.avg_score from ( select sid from student where sid not in ( select student_id from score where course_id = 2 ) ) as t1, ( select avg(score) as avg_score from score where course_id = 2 ) as t2; #27、按平均成绩从低到高显示所有学生的“语文”、“数学”、“音乐”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,音乐,有效课程数,有效平均分； # **** select sc.student_id, (select score.score from score left join course on score.course_id = course.cid where course.cname = '语文' and score.student_id = sc.student_id) as yw, (select score.score from score left join course on score.course_id = course.cid where course.cname = '数学' and score.student_id = sc.student_id) as sx, (select score.score from score left join course on score.course_id = course.cid where course.cname = '音乐' and score.student_id = sc.student_id) as yy, count(sc.course_id), avg(sc.score) from score as sc group by sc.student_id order by avg(sc.score) asc; #28、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 course.cid, max(score.score) as max_score, min(score.score) as min_score from course left join score on course.cid = score.course_id group by score.course_id; #29、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 course_id, avg(score) as avg_score, sum(case when score.score > 60 then 1 else 0 end) / count(1) * 100 as percent from score group by course_id order by avg(score) asc, percent desc; #30、课程平均分从高到低显示（显示任课老师）； select t1.course_id, t1.avg_score, teacher.tname from course, teacher, ( select course_id, avg(score) as avg_score from score group by course_id order by avg_score desc ) as t1 where course.cid = t1.course_id and course.teacher_id = teacher.tid order by t1.avg_score desc; #31、查询各科成绩前三名的记录(不考虑成绩并列情况) # 和44题相似！！ select score.sid, score.student_id, score.course_id, score.score, t1.first_score, t1.second_score, t1.third_score from score inner join ( select s1.sid, (select score from score as s2 where s1.course_id = s2.course_id order by score desc limit 0,1) as first_score, (select score from score as s3 where s1.course_id = s3.course_id order by score desc limit 1,1) as second_score, (select score from score as s4 where s1.course_id = s4.course_id order by score desc limit 2,1) as third_score from score as s1 ) as t1 on score.sid = t1.sid where score.score in ( t1.first_score, t1.second_score, t1.third_score ); #32、查询每门课程被选修的学生数； select # 包含了没有被选修的课程显示0 course.cid, ifnull(t1.count_students,0) as count_student from course left join ( select course_id, count(student_id) as count_students from score group by course_id ) as t1 on course.cid = t1.course_id; #33、查询选修了2门以上课程的全部学生的学号和姓名； select sid, sname from student where sid in ( select student_id from score group by student_id having count(course_id) > 2 ); #34、查询男生、女生的人数，按倒序排列； select gender, count(sid) as count_student from student group by gender order by count_student desc; #35、查询姓“张”的学生名单； select student.sid, student.sname, student.gender, class.caption from student inner join class on student.class_id = class.cid where student.sname like '张%'; #36、查询同名同姓学生名单，并统计同名人数； select sname, count(sname) as count_sname from student group by sname having count(sname) > 1; #37、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列； select course_id, avg(score) as avg_score from score group by course_id order by avg_score, course_id desc; #38、查询课程名称为“数学”，且分数低于60的学生姓名和分数； select student.sname, t1.score from student inner join ( select score.student_id, score.score from score inner join course on score.course_id = course.cid where course.cname = '数学' and score.score < 60 ) as t1 on student.sid = t1.student_id; #39、查询课程编号为“3”且课程成绩在80分以上的学生的学号和姓名； select sid, sname from student where sid in ( select student_id from score where course_id = 3 and score > 80 ); #40、求选修了课程的学生人数 select course_id, count(student_id) as count_student from score group by course_id; #41、查询选修“王五”老师所授课程的学生中，成绩最高和最低的学生姓名及其成绩； select # 教的课可能包含多门，按课程id来分的！包含了最高，最低成绩相等的情况 student.sname, t2.course_id, t2.score, t2.max_score, t2.min_score from student inner join ( select score.student_id, score.course_id, score.score, t1.max_score, t1.min_score from score, ( select course_id, max(score) as max_score , min(score) as min_score from score where course_id in ( select cid from course inner join teacher on course.teacher_id = teacher.tid where teacher.tname = '王五' ) group by course_id ) as t1 where score.course_id = t1.course_id and score.score in ( max_score, min_score ) ) as t2 on student.sid = t2.student_id; #42、查询各个课程及相应的选修人数； select # 包含了没有被选修的课程显示0 course.cname, ifnull(t1.count_student,0) as count_student from course left join ( select course_id, count(student_id) as count_student from score group by course_id ) as t1 on course.cid = t1.course_id; #43、查询不同课程但成绩相同的学生的学号、课程号、学生成绩； select distinct # 不同的学生之间，成绩相同 这里有问题！！ s1.student_id, s2.student_id, s1.course_id as s1_course_id, s2.course_id as s2_course_id, s1.score, s2.score from score as s1, score as s2 where s1.course_id != s2.course_id and s1.score = s2.score; select distinct # 同一个学生，成绩相同 s1.student_id, s2.student_id, s1.course_id as s1_course_id, s2.course_id as s2_course_id, s1.score, s2.score from score as s1, score as s2 where s1.student_id = s2.student_id and s1.course_id != s2.course_id and s1.score = s2.score; #44、查询每门课程成绩最好的前两名学生id和姓名； #??? 这里有个问题,成绩相同的学生，会都录入！！ select student.sid, student.sname, t2.course_id, t2.score, t2.first_score, t2.second_score from student inner join ( # 这里会出现成绩相同的情况，录入了超过了两名的学生！！ select score.student_id, score.course_id, score.score, t1.first_score, t1.second_score from score inner join ( select s1.sid, (select s2.score from score as s2 where s1.course_id = s2.course_id order by s2.score desc limit 0,1) as first_score, (select s3.score from score as s3 where s1.course_id = s3.course_id order by s3.score desc limit 1,1) as second_score from score as s1 ) as t1 on score.sid = t1.sid where score.score in ( # ？？在这，会超过两个！！ t1.first_score, t1.second_score ) ) as t2 on student.sid = t2.student_id; ************************************************************** # 这个有排名 包括了成绩相同的！ select c.sname, d.cname, a.score from score a inner join ( select course_id, score, rank from ( select a.course_id, a.score, count(*) as rank from (select course_id, score from score group by course_id, score order by course_id, score desc) a inner join (select course_id, score from score group by course_id, score order by course_id, score desc) b on a.course_id = b.course_id and a.score <= b.score group by course_id, score ) t1 where rank in (1, 2) order by course_id, rank ) b on a.course_id = b.course_id and a.score = b.score inner join student c on a.student_id = c.sid inner join course d on a.course_id = d.cid; ************************************************************** #45、检索至少选修两门课程的学生学号； select student_id from score group by student_id having count(course_id) >= 2; #46、查询没有学生选修的课程的课程号和课程名； select cid, cname from course where cid not in ( select course_id from score group by course_id ); #47、查询没带过任何班级的老师id和姓名； select tid, tname from teacher where tid not in ( select tid from teach2cls group by tid ); #48、查询有两门以上课程超过80分的学生id及其平均成绩； select student_id, avg(score) as avg_score from score where student_id in ( select student_id from score where score > 80 group by student_id having count(course_id) > 2 ) group by student_id; #49、检索“3”课程分数小于60，按分数降序排列的同学学号； select student_id, score from score where course_id = 3 and score < 60 order by score desc; #50、删除编号为“2”的同学的“1”课程的成绩； delete from # 需要在包一层select(),否则 You can't specify target table 'score' for update in FROM clause score where sid = ( select t1.sid from ( select sid from score where student_id = 2 and course_id = 1 ) as t1 ); #51、查询同时选修了物理课和生物课的学生id和姓名； select sid, sname from student where sid in ( select student_id from score where course_id in ( select cid from course where course.cname in ( '物理', '生物' ) ) group by student_id having count(course_id) = 2 );