数据库学习
CREATE TABLE `class` (
`cid` int(11) NOT NULL AUTO_INCREMENT,
`caption` varchar(32) NOT NULL,
PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of `class`
-- ----------------------------
BEGIN;
INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班');
COMMIT;
-- ----------------------------
-- Table structure for `course`
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
`cid` int(11) NOT NULL AUTO_INCREMENT,
`cname` varchar(32) NOT NULL,
`teacher_id` int(11) NOT NULL,
PRIMARY KEY (`cid`),
KEY `fk_course_teacher` (`teacher_id`),
CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of `course`
-- ----------------------------
BEGIN;
INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2');
COMMIT;
-- ----------------------------
-- Table structure for `score`
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
`sid` int(11) NOT NULL AUTO_INCREMENT,
`student_id` int(11) NOT NULL,
`course_id` int(11) NOT NULL,
`num` int(11) NOT NULL,
PRIMARY KEY (`sid`),
KEY `fk_score_student` (`student_id`),
KEY `fk_score_course` (`course_id`),
CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`),
CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of `score`
-- ----------------------------
BEGIN;
INSERT INTO `score` VALUES ('1', '1', '1', '10'), ('2', '1', '2', '9'), ('5', '1', '4', '66'), ('6', '2', '1', '8'), ('8', '2', '3', '68'), ('9', '2', '4', '99'), ('10', '3', '1', '77'), ('11', '3', '2', '66'), ('12', '3', '3', '87'), ('13', '3', '4', '99'), ('14', '4', '1', '79'), ('15', '4', '2', '11'), ('16', '4', '3', '67'), ('17', '4', '4', '100'), ('18', '5', '1', '79'), ('19', '5', '2', '11'), ('20', '5', '3', '67'), ('21', '5', '4', '100'), ('22', '6', '1', '9'), ('23', '6', '2', '100'), ('24', '6', '3', '67'), ('25', '6', '4', '100'), ('26', '7', '1', '9'), ('27', '7', '2', '100'), ('28', '7', '3', '67'), ('29', '7', '4', '88'), ('30', '8', '1', '9'), ('31', '8', '2', '100'), ('32', '8', '3', '67'), ('33', '8', '4', '88'), ('34', '9', '1', '91'), ('35', '9', '2', '88'), ('36', '9', '3', '67'), ('37', '9', '4', '22'), ('38', '10', '1', '90'), ('39', '10', '2', '77'), ('40', '10', '3', '43'), ('41', '10', '4', '87'), ('42', '11', '1', '90'), ('43', '11', '2', '77'), ('44', '11', '3', '43'), ('45', '11', '4', '87'), ('46', '12', '1', '90'), ('47', '12', '2', '77'), ('48', '12', '3', '43'), ('49', '12', '4', '87'), ('52', '13', '3', '87');
COMMIT;
-- ----------------------------
-- Table structure for `student`
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`sid` int(11) NOT NULL AUTO_INCREMENT,
`gender` char(1) NOT NULL,
`class_id` int(11) NOT NULL,
`sname` varchar(32) NOT NULL,
PRIMARY KEY (`sid`),
KEY `fk_class` (`class_id`),
CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of `student`
-- ----------------------------
BEGIN;
INSERT INTO `student` VALUES ('1', '男', '1', '理解'), ('2', '女', '1', '钢蛋'), ('3', '男', '1', '张三'), ('4', '男', '1', '张一'), ('5', '女', '1', '张二'), ('6', '男', '1', '张四'), ('7', '女', '2', '铁锤'), ('8', '男', '2', '李三'), ('9', '男', '2', '李一'), ('10', '女', '2', '李二'), ('11', '男', '2', '李四'), ('12', '女', '3', '如花'), ('13', '男', '3', '刘三'), ('14', '男', '3', '刘一'), ('15', '女', '3', '刘二'), ('16', '男', '3', '刘四');
COMMIT;
-- ----------------------------
-- Table structure for `teacher`
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
`tid` int(11) NOT NULL AUTO_INCREMENT,
`tname` varchar(32) NOT NULL,
PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of `teacher`
-- ----------------------------
BEGIN;
INSERT INTO `teacher` VALUES ('1', '张磊老师'), ('2', '李平老师'), ('3', '刘海燕老师'), ('4', '朱云海老师'), ('5', '李杰老师');
COMMIT;
SET FOREIGN_KEY_CHECKS = 1;
表结构和数据
题目：
2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
1)
select A.student_id,生物分数,物理分数 from
(select student_id,num as 生物分数
from score
where course_id=(select cid from course where cname='生物')) as A
left join
(select student_id,num as 物理分数
from score
where course_id=(select cid from course where cname='物理')) as B
on A.student_id = B.student_id where 生物分数 > if(isnull(物理分数),0,物理分数);
2)
select A.student_id,生物分数,物理分数 from
(select student_id,num as 生物分数 from score left join course on score.course_id = course.cid where course.cname = '生物') as A
left join
(select student_id,num as 物理分数 from score left join course on score.course_id = course.cid where course.cname = '物理') as B
on A.student_id = B.student_id where 生物分数 > if(isnull(物理分数),0,物理分数);
3、查询平均成绩大于60分的同学的学号和平均成绩；
select student_id,avg(num) as 平均成绩 from score group by student_id having 平均成绩 > 60;
4、查询所有同学的学号、姓名、选课数、总成绩；
select student.sid,sname,count(student_id),sum(num)
from score right join student
on student.sid=student_id
group by student_id;
5、查询姓“李”的老师的个数；
select count(*) from teacher where tname like '李%';
6、查询没学过“李平老师”老师课的同学的学号、姓名；
select distinct student.sid,sname from student where sid not in (
select distinct student_id
from score
where course_id in(
select cid
from course left join teacher
on course.teacher_id=teacher.tid
where tname = '李平老师')
);
7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
1)
select A.sid,A.sname from
(select student.sid,sname from score right join student
on student.sid=student_id
where course_id='001') as A
inner join
(select student.sid,sname from score right join student
on student.sid=student_id
where course_id='002') as B
on A.sid=B.sid
2)
select student_id,sname from
(select student_id,course_id from score where course_id = 1 or course_id = 2) as B
left join student on B.student_id = student.sid group by student_id HAVING count(student_id) > 1
8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
select student.sid,sname from score right join student
on student.sid=student_id
where course_id in(
select cid from course left join teacher
on course.teacher_id=teacher.tid
where tname='李平老师'
) group by student.sid HAVING count(student.sid) = (
select count(cid) from course left join teacher
on course.teacher_id=teacher.tid
where tname='李平老师'
);
9、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；
select sname,sid from student inner join (
select A.student_id from
(select student_id,num as s1 from score left join course on score.course_id = course.cid where course.cid = '001') as A
left join
(select student_id,num as s2 from score left join course on score.course_id = course.cid where course.cid = '002') as B
on A.student_id = B.student_id where s1 > if(isnull(s2),0,s2)
) as C
on C.student_id=student.sid;
10、查询有课程成绩小于60分的同学的学号、姓名；
select distinct student.sid,sname from student left join score
on student.sid=score.student_id
where num<60;
11、查询没有学全所有课的同学的学号、姓名；
select student.sid,sname from score right join student
on student.sid=score.student_id
group by student_id
having count(student_id) != (
select count(*) from course
);
12、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名；
select student.sid,sname,count(sname) from score right join student
on student.sid=student_id
where student_id !='001' and course_id in (
select course_id from score where student_id='001'
) group by student_id;
13、查询至少学过学号为“001”同学所有课的其他同学学号和姓名；
select student.sid,sname from score right join student
on student.sid=student_id
where student_id !='001' and course_id in (
select course_id from score where student_id='001'
) group by student_id
having count(sname) >= (
select count(*) from score
where student_id='001');
14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名；
select student.sid,sname from score right join student
on student.sid=student_id where student_id in(
select student_id from score where student_id != 2 group by student_id HAVING count(course_id) = (select count(course_id) from score where student_id = 2))
and course_id in (
select course_id from score where student_id='002'
) group by student_id
having count(course_id) = (
select count(course_id) from score
where student_id='002');
15、删除学习“叶平”老师课的score表记录；
delete from score where course_id in (
select cid from course left join teacher on course.teacher_id=tid where tname='李平老师'
)
16、向SC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“002”课程的同学学号；②插入“002”号课程的平均成绩；
insert into score(student_id, course_id, num) select sid,2,(select avg(num) from score where course_id = 2)
from student where sid not in (
select student_id from score where course_id = 2
)
17、按平均成绩从低到高 显示所有学生的“生物”、“物理”、“体育”、“美术”4门的课程成绩，按如下形式显示：学生ID,生物,物理,体育,美术,有效课程数,有效平均分；（不会这种查询语法）
select student_id,
(select num from score s left join course c on s.course_id=c.cid where cname='生物' and sc.student_id=s.student_id) as 生物分数,
(select num from score s left join course c on s.course_id=c.cid where cname='物理' and sc.student_id=s.student_id) as 物理分数,
(select num from score s left join course c on s.course_id=c.cid where cname='体育' and sc.student_id=s.student_id) as 体育分数,
(select num from score s left join course c on s.course_id=c.cid where cname='美术' and sc.student_id=s.student_id)as 美术分数,
count(course_id),avg(num)
from score sc
group by student_id
order by avg(num);
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 course_id,max(num),min(num) from score group by course_id;
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；
1)
select avg(num),score.course_id,课程人数,课程及格人数,(课程及格人数/课程人数*100) as 及格率 from score left join
(select course_id,count(student_id) as 课程人数 from score group by course_id order by course_id) as A
on score.course_id=A.course_id
left join
(select course_id,count(student_id) as 课程及格人数 from score where num >=60 group by course_id order by course_id) as B
on A.course_id=B.course_id
group by score.course_id
having
order by avg(num),及格率 desc;
2)
select course_id, avg(num) as avgnum,sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent from score group by course_id order by avgnum asc,percent desc;
20、课程平均分从高到低显示（现实任课老师）；
select tname,avg(课程平均分) from
(select tname,c.cid from teacher t right join course c on t.tid=c.teacher_id) as A
left join
(select avg(num) as 课程平均分,course_id from score group by course_id order by avg(num) desc) as B
on A.cid=B.course_id
group by tname
order by avg(课程平均分) desc;
21、查询各科成绩前5名的记录:(不考虑成绩并列情况)；
select distinct cname,course_id,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 2,1) as third_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 3,1) as fourth_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 4,1) as fifth_num
from score s1 left join course c on c.cid=s1.course_id;
22、查询每门课程被选修的学生数；
select course_id,count(student_id) from score group by course_id;
23、查询出只选修了一门课程的全部学生的学号和姓名；
select student_id,sname from student st left join score sc on st.sid=sc.student_id
group by student_id
having count(course_id)=1;
27、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(if(isnull(num),0,num)) from score group by course_id order by avg(num),course_id desc;
28、查询平均成绩大于85的所有学生的学号、姓名和平均成绩；
select student_id,sname,avg(num) from score sc left join student st on sc.student_id=st.sid group by student_id;
29、查询课程名称为“生物”，且分数低于60的学生姓名和分数；
select sname,num from score sc left join student st on sc.student_id=st.sid
left join course c on c.cid=sc.course_id
where c.cname='生物' and num<60;
31、求选了课程的学生人数
select count(distinct student_id) from score
32、查询选修“张磊老师”老师所授课程的学生中，成绩最高的学生姓名及其成绩；
select sname,max(num) from score sc
left join student st on sc.student_id=st.sid
where course_id in (
select cid from course c
left join teacher t on c.teacher_id=t.tid
where tname='张磊老师'
);
33、查询各个课程及相应的选修人数；
select cname,count(student_id) from score sc
left join course c on c.cid=sc.course_id
group by course_id;
34、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 student_id,course_id,num from score where sid in (
select s1.sid from score s1
inner join score s2 on s1.num=s2.num and s1.course_id != s2.course_id)
35、查询每门课程成绩最好的前两名；
select distinct cname,course_id,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num
from score s1 left join course c on c.cid=s1.course_id;
36、检索至少选修两门课程的学生学号；
select student_id from score sc group by student_id having count(course_id)>1;
37、查询全部学生都选修的课程的课程号和课程名；
select course_id,cname from score sc
right join course c on c.cid=sc.course_id
group by course_id
having count(student_id)=(
select count(distinct sid) from student
);
38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；
select dictinct sname from score sc
left join student st on sc.student_id=st.sid
where student_id not in (
select student_id from score where course_id in (
select cid from course c left join teacher t on c.teacher_id=t.tid where tname='张磊老师'
)
);
39、查询两门以上不及格课程的同学的学号及其平均成绩；
select student_id,avg(num) from score where student_id in (
select student_id from score where num<60 group by student_id having count(course_id)>1
) group by student_id;
40、检索“004”课程分数小于60，按分数降序排列的同学学号；
select student_id from score where course_id=4 and num<60 order by num desc;
