MySql练习题参考答案

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 Target Server Version : 50624
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 Date: 10/21/2016 06:46:46 AM

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                SET
                 NAMES utf8;

                SET FOREIGN_KEY_CHECKS =0;

-- ----------------------------
--  Table structure for `class`
-- ----------------------------DROPTABLEIFEXISTS `class`;
CREATETABLE `class` (
  `cid` int(11) NOTNULL AUTO_INCREMENT,
  `caption` varchar(32) NOTNULL,
  PRIMARYKEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `class`
-- ----------------------------BEGIN;
INSERTINTO `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`
-- ----------------------------DROPTABLEIFEXISTS `course`;
CREATETABLE `course` (
  `cid` int(11) NOTNULL AUTO_INCREMENT,
  `cname` varchar(32) NOTNULL,
  `teacher_id` int(11) NOTNULL,
  PRIMARYKEY (`cid`),
  KEY `fk_course_teacher` (`teacher_id`),
  CONSTRAINT `fk_course_teacher` FOREIGNKEY (`teacher_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=5DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `course`
-- ----------------------------BEGIN;
INSERTINTO `course` VALUES (‘1‘, ‘生物‘, ‘1‘), (‘2‘, ‘物理‘, ‘2‘), (‘3‘, ‘体育‘, ‘3‘), (‘4‘, ‘美术‘, ‘2‘);
COMMIT;

-- ----------------------------
--  Table structure for `score`
-- ----------------------------DROPTABLEIFEXISTS `score`;
CREATETABLE `score` (
  `sid` int(11) NOTNULL AUTO_INCREMENT,
  `student_id` int(11) NOTNULL,
  `course_id` int(11) NOTNULL,
  `num` int(11) NOTNULL,
  PRIMARYKEY (`sid`),
  KEY `fk_score_student` (`student_id`),
  KEY `fk_score_course` (`course_id`),
  CONSTRAINT `fk_score_course` FOREIGNKEY (`course_id`) REFERENCES `course` (`cid`),
  CONSTRAINT `fk_score_student` FOREIGNKEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=53DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `score`
-- ----------------------------BEGIN;
INSERTINTO `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`
-- ----------------------------DROPTABLEIFEXISTS `student`;
CREATETABLE `student` (
  `sid` int(11) NOTNULL AUTO_INCREMENT,
  `gender` char(1) NOTNULL,
  `class_id` int(11) NOTNULL,
  `sname` varchar(32) NOTNULL,
  PRIMARYKEY (`sid`),
  KEY `fk_class` (`class_id`),
  CONSTRAINT `fk_class` FOREIGNKEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=17DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `student`
-- ----------------------------BEGIN;
INSERTINTO `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`
-- ----------------------------DROPTABLEIFEXISTS `teacher`;
CREATETABLE `teacher` (
  `tid` int(11) NOTNULL AUTO_INCREMENT,
  `tname` varchar(32) NOTNULL,
  PRIMARYKEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=6DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `teacher`
-- ----------------------------BEGIN;
INSERTINTO `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

表结构和数据

                2
                、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
思路：
    获取所有有生物课程的人（学号，成绩） 
                -
                 临时表
    获取所有有物理课程的人（学号，成绩） 
                -
                 临时表
    根据【学号】连接两个临时表：
        学号  物理成绩   生物成绩
 
    然后再进行筛选
 
        
                select A.student_id,sw,ty from
 
        (select student_id,num as sw from score leftjoin course on score.course_id = course.cid where course.cname =‘生物‘) as A
 
        leftjoin
 
        (select student_id,num  as ty from score leftjoin course on score.course_id = course.cid where course.cname =‘体育‘) as B
 
        on A.student_id = B.student_id where sw >if(isnull(ty),0,ty);
 
3、查询平均成绩大于60分的同学的学号和平均成绩；
    思路：
        根据学生分组，使用avg获取平均值，通过having对avg进行筛选
 
        select student_id,avg(num) from score groupby student_id havingavg(num) >604、查询所有同学的学号、姓名、选课数、总成绩；
 
    select score.student_id,sum(score.num),count(score.student_id),student.sname
    from
        score leftjoin student on score.student_id = student.sid  
    groupby score.student_id
 
5、查询姓“李”的老师的个数；
    selectcount(tid) from teacher where tname like‘李%‘selectcount(1) from (select tid from teacher where tname like‘李%‘) as B
 
6、查询没学过“叶平”老师课的同学的学号、姓名；
    思路：
        先查到“李平老师”老师教的所有课ID
        获取选过课的所有学生ID
        学生表中筛选
    select*from student where sid notin (
        selectDISTINCT student_id from score where score.course_id in (
            select cid from course leftjoin 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；
    思路：
        先查到既选择001又选择002课程的所有同学
        根据学生进行分组，如果学生数量等于2表示，两门均已选择
 
    select student_id,sname from
 
    (select student_id,course_id from score where course_id =1or course_id =2) as B
      
    leftjoin student on B.student_id = student.sid groupby student_id HAVINGcount(student_id) >18、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
 
    同上，只不过将001和002变成 in (叶平老师的所有课)
 
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；
    同第1题
 
 
10、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 (
        selectdistinct student_id from score where num <60
    )
 
11、查询没有学全所有课的同学的学号、姓名；
    思路：
        在分数表中根据学生进行分组，获取每一个学生选课数量
        如果数量 == 总课程数量，表示已经选择了所有课程
 
        select student_id,sname
        from score leftjoin student on score.student_id = student.sid
        groupby student_id HAVINGcount(course_id) = (selectcount(1) 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；
    思路：
        获取 001 同学选择的所有课程
        获取课程在其中的所有人以及所有课程
        根据学生筛选，获取所有学生信息
        再与学生表连接，获取姓名
 
        select student_id,sname, count(course_id)
        from score leftjoin student on score.student_id = student.sid
        where student_id !=1and course_id in (select course_id from score where student_id =1) groupby 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；
        先找到和001的学过的所有人
        然后个数 ＝ 001所有学科     ＝＝》 其他人可能选择的更多
 
        select student_id,sname, count(course_id)
        from score leftjoin student on score.student_id = student.sid
        where student_id !=1and course_id in (select course_id from score where student_id =1) groupby student_id havingcount(course_id) ＝ (selectcount(course_id) from score where student_id =1)
 
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；
         
        个数相同
        002学过的也学过
 
        select student_id,sname from score leftjoin student on score.student_id = student.sid where student_id in (
            select student_id from score  where student_id !=1groupby student_id HAVINGcount(course_id) = (selectcount(1) from score where student_id =1)
        ) and course_id in (select course_id from score where student_id =1) groupby student_id HAVINGcount(course_id) = (selectcount(1) from score where student_id =1)
 
 
15、删除学习“叶平”老师课的score表记录；
 
    deletefrom score where course_id in (
        select cid from course leftjoin teacher on course.teacher_id = teacher.tid where teacher.name =‘叶平‘
    )
 
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；
    思路：
        由于insert 支持 
                inset into tb1(xx,xx) select x1,x2 from tb2;
        所有，获取所有没上过002课的所有人，获取002的平均成绩
 
    insertinto score(student_id, course_id, num) select sid,2,(selectavg(num) from score where course_id =2)
    from student where sid notin (
        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“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；
    select sc.student_id,
        (select num from score leftjoin course on score.course_id = course.cid where course.cname = "生物" and score.student_id=sc.student_id) as sy,
        (select num from score leftjoin course on score.course_id = course.cid where course.cname = "物理" and score.student_id=sc.student_id) as wl,
        (select num from score leftjoin course on score.course_id = course.cid where course.cname = "体育" and score.student_id=sc.student_id) as ty,
        count(sc.course_id),
        avg(sc.num)
    from score as sc
    groupby student_id desc18、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) as max_num, min(num) as min_num from score groupby 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；
    思路：casewhen .. thenselect course_id, avg(num) as avgnum,sum(casewhen score.num >60then1else0END)/count(1)*100aspercentfrom score groupby course_id orderby avgnum asc,percentdesc;
 
20、课程平均分从高到低显示（现实任课老师）；
 
    selectavg(if(isnull(score.num),0,score.num)),teacher.tname from course
    leftjoin score on course.cid = score.course_id
    leftjoin teacher on course.teacher_id = teacher.tid
 
    groupby score.course_id
 
 
21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
    select score.sid,score.course_id,score.num,T.first_num,T.second_num from score leftjoin
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id orderby num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id orderby num desc limit 3,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num
 
22、查询每门课程被选修的学生数；
     
    select course_id, count(1) from score groupby 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.sid, student.sname, count(1) from score
 
    leftjoin student on score.student_id  = student.sid
 
     groupby course_id havingcount(1) =124、查询男生、女生的人数；
    select*from
    (selectcount(1) as man from student where gender=‘男‘) as A ,
    (selectcount(1) as feman from student where gender=‘女‘) as B
 
25、查询姓“张”的学生名单；
    select sname from student where sname like‘张%‘;
 
26、查询同名同姓学生名单，并统计同名人数；
 
    select sname,count(1) ascountfrom student groupby sname;
 
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)) asavgfrom score groupby course_id orderbyavgasc,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(if(isnull(num), 0 ,num)) from score leftjoin student on score.student_id = student.sid groupby student_id;
 
29、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,score.num from score
    leftjoin course on score.course_id = course.cid
    leftjoin student on score.student_id = student.sid
    where score.num <60and course.cname =‘生物‘30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
    select*from score where score.student_id =3and score.num >8031、求选了课程的学生人数
 
    selectcount(distinct student_id) from score
 
    selectcount(c) from (
        selectcount(student_id) as c from score groupby student_id) as A
 
32、查询选修“杨艳”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,num from score
    leftjoin student on score.student_id = student.sid
    where score.course_id in (select course.cid from course leftjoin teacher on course.teacher_id = teacher.tid where tname=‘张磊老师‘) orderby num desc limit 1;
 
33、查询各个课程及相应的选修人数；
    select course.cname,count(1) from score
    leftjoin course on score.course_id = course.cid
    groupby 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；
    selectDISTINCT s1.course_id,s2.course_id,s1.num,s2.num from score as s1, score as s2 where 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 score.sid,score.course_id,score.num,T.first_num,T.second_num from score leftjoin
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id orderby num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id orderby num desc limit 1,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num
 
36、检索至少选修两门课程的学生学号；
    select student_id from score groupby student_id havingcount(student_id) >137、查询全部学生都选修的课程的课程号和课程名；
    select course_id,count(1) from score groupby course_id havingcount(1) = (selectcount(1) 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 student_id,student.sname from score
    leftjoin student on score.student_id = student.sid
    where score.course_id notin (
        select cid from course leftjoin teacher on course.teacher_id = teacher.tid where tname =‘张磊老师‘
    )
    groupby student_id
 
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,count(1) from score where num <60groupby student_id havingcount(1) >240、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 num<60and course_id =4orderby num desc;
 
41、删除“002”同学的“001”课程的成绩；
    deletefrom score where course_id =1and student_id =2