作业
#各原表信息：
# 班级表***********************************
mysql> select * from class;
+-----+----------+
| cid | caption |
+-----+----------+
| 1 | 三年二班 |
| 2 | 一年三班 |
| 3 | 三年一班 |
| 4 | 二年一班 |
+-----+----------+
# 学生表***********************************
mysql> select * from student;
+-----+--------+--------+----------+
| sid | sname | gender | class_id |
+-----+--------+--------+----------+
| 1 | 钢蛋 | 女 | 1 |
| 2 | 铁锤 | 女 | 1 |
| 3 | 山炮 | 男 | 2 |
| 4 | 张三 | 男 | 4 |
| 5 | 李四 | 男 | 3 |
| 6 | 哪吒 | 男 | 1 |
| 7 | 小龙女 | 女 | 2 |
| 8 | 申公豹 | 男 | 3 |
| 9 | 邓婵玉 | 女 | 4 |
+-----+--------+--------+----------+
# 老师表***********************************
mysql> select * from teacher;
+-----+--------+
| tid | tname |
+-----+--------+
| 1 | 李修元 |
| 2 | 叶平 |
| 3 | 李元霸 |
| 4 | 陈世美 |
| 5 | 姜子牙 |
| 6 | 韩立 |
+-----+--------+
# 课程表***********************************
mysql> select * from course;
+-----+--------+------------+
| cid | cname | teacher_id |
+-----+--------+------------+
| 1 | 生物 | 1 |
| 2 | 物理 | 2 |
| 3 | 化学 | 3 |
| 4 | 体育 | 4 |
| 5 | 数学 | 5 |
| 6 | 语文 | 6 |
| 7 | 英语 | 2 |
| 8 | 政治 | 3 |
| 9 | 历史 | 4 |
| 10 | python | 1 |
+-----+--------+------------+
# 成绩表***********************************
mysql> select * from score;
+-----+------------+-----------+--------+
| sid | student_id | course_id | number |
+-----+------------+-----------+--------+
| 1 | 1 | 1 | 60 |
| 2 | 1 | 2 | 80 |
| 3 | 2 | 2 | 100 |
| 4 | 3 | 3 | 58 |
| 5 | 4 | 5 | 70 |
| 6 | 5 | 4 | 90 |
| 7 | 6 | 6 | 88 |
| 8 | 7 | 8 | 40 |
| 9 | 8 | 9 | 58 |
| 10 | 9 | 10 | 71 |
| 11 | 1 | 5 | 61 |
| 12 | 2 | 4 | 65 |
| 13 | 3 | 9 | 84 |
| 14 | 4 | 7 | 96 |
| 15 | 5 | 2 | 93 |
| 16 | 6 | 8 | 89 |
+-----+------------+-----------+--------+
1. 查询所有大于60分的学生的姓名和学号 (DISTINCT: 去重)
mysql> select distinct student.sid, sname from student right join score on stude
nt.sid = student_id where number >60 order by student.sid;
+------+--------+
| sid | sname |
+------+--------+
| 1 | 钢蛋 |
| 2 | 铁锤 |
| 3 | 山炮 |
| 4 | 张三 |
| 5 | 李四 |
| 6 | 哪吒 |
| 9 | 邓婵玉 |
+------+--------+
7 rows in set (0.00 sec)
-- 2.查询每个老师教授的课程数量 和 老师信息
mysql> select tid ,tname, count(cname) from teacher left join course on tid = teacher_id group by tid , tname;
+-----+--------+--------------+
| tid | tname | count(cname) |
+-----+--------+--------------+
| 1 | 李修元 | 2 |
| 2 | 叶平 | 2 |
| 3 | 李元霸 | 2 |
| 4 | 陈世美 | 2 |
| 5 | 姜子牙 | 1 |
| 6 | 韩立 | 1 |
+-----+--------+--------------+
6 rows in set (0.00 sec)
-- 3. 查询学生的信息以及学生所在的班级信息
mysql> select sid , sname , gender , caption from student left join class on cid = class_id ;
+-----+--------+--------+----------+
| sid | sname | gender | caption |
+-----+--------+--------+----------+
| 1 | 钢蛋 | 女 | 三年二班 |
| 2 | 铁锤 | 女 | 三年二班 |
| 6 | 哪吒 | 男 | 三年二班 |
| 3 | 山炮 | 男 | 一年三班 |
| 7 | 小龙女 | 女 | 一年三班 |
| 5 | 李四 | 男 | 三年一班 |
| 8 | 申公豹 | 男 | 三年一班 |
| 4 | 张三 | 男 | 二年一班 |
| 9 | 邓婵玉 | 女 | 二年一班 |
+-----+--------+--------+----------+
9 rows in set (0.00 sec)
-- 4、学生中男生的个数和女生的个数
mysql> select gender , count(gender) from student group by gender;
+--------+---------------+
| gender | count(gender) |
+--------+---------------+
| 女 | 4 |
| 男 | 5 |
+--------+---------------+
2 rows in set (0.00 sec)
-- 5、获取所有学习'生物'的学生的学号和成绩；姓名
mysql> select student.sid , sname , number from student left join score on
-> student.sid = student_id left join course on cid = course_id
-> where cname = '生物';
+-----+-------+--------+
| sid | sname | number |
+-----+-------+--------+
| 1 | 钢蛋 | 60 |
+-----+-------+--------+
1 row in set (0.00 sec)
-- 6、查询平均成绩大于60分的同学的学号和平均成绩；
mysql> select student.sid , sname ,avg(number) from student left join score on s
tudent.sid=student_id
-> group by student.sid having avg(number)>60;
+-----+--------+-------------+
| sid | sname | avg(number) |
+-----+--------+-------------+
| 1 | 钢蛋 | 67.0000 |
| 2 | 铁锤 | 82.5000 |
| 3 | 山炮 | 71.0000 |
| 4 | 张三 | 83.0000 |
| 5 | 李四 | 91.5000 |
| 6 | 哪吒 | 88.5000 |
| 9 | 邓婵玉 | 71.0000 |
+-----+--------+-------------+
7 rows in set (0.00 sec)
-- 7、查询姓“李”的老师的个数；
mysql> select count(tname) from teacher
-> where tname like '李%';
+--------------+
| count(tname) |
+--------------+
| 2 |
+--------------+
1 row in set (0.00 sec)
-- 8、查询课程成绩小于60分的同学的学号、姓名；
mysql> select student.sid , sname,number from student left join score on student
.sid =
-> student_id
-> where number < 60;
+-----+--------+--------+
| sid | sname | number |
+-----+--------+--------+
| 3 | 山炮 | 58 |
| 7 | 小龙女 | 40 |
| 8 | 申公豹 | 58 |
+-----+--------+--------+
3 rows in set (0.00 sec)
-- 9. 删除学习“叶平”老师课的SC表记录
mysql> delete from score
-> where course_id in (select cid from course left join teacher on
-> teacher_id = tid
-> where tname = '叶平');
Query OK, 4 rows affected (0.10 sec)
-- 10.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；
mysql> select course_id ,max(number) , min(number)
-> from score
-> group by course_id;
+-----------+-------------+-------------+
| course_id | max(number) | min(number) |
+-----------+-------------+-------------+
| 1 | 60 | 60 |
| 2 | 100 | 80 |
| 3 | 58 | 58 |
| 4 | 90 | 65 |
| 5 | 70 | 61 |
| 6 | 88 | 88 |
| 7 | 96 | 96 |
| 8 | 89 | 40 |
| 9 | 84 | 58 |
| 10 | 71 | 71 |
+-----------+-------------+-------------+
10 rows in set (0.00 sec)
-- 11.查询每门课程被选修的学生数
mysql> select course_id ,cname, count(student_id) from score left join course on
-> course_id = course.cid
-> group by course_id , cname;
+-----------+--------+-------------------+
| course_id | cname | count(student_id) |
+-----------+--------+-------------------+
| 1 | 生物 | 1 |
| 2 | 物理 | 3 |
| 3 | 化学 | 1 |
| 4 | 体育 | 2 |
| 5 | 数学 | 2 |
| 6 | 语文 | 1 |
| 7 | 英语 | 1 |
| 8 | 政治 | 2 |
| 9 | 历史 | 2 |
| 10 | python | 1 |
+-----------+--------+-------------------+
10 rows in set (0.00 sec)
-- 12.查询姓“张”的学生名单；
mysql> select * from student where sname like '张%';
+-----+-------+--------+----------+
| sid | sname | gender | class_id |
+-----+-------+--------+----------+
| 4 | 张三 | 男 | 4 |
+-----+-------+--------+----------+
1 row in set (0.00 sec)
-- 13.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
mysql> select course_id , cname ,avg(number) from score left join course
-> on course_id = course.cid
-> group by course_id , cname
-> order by avg(number) ,course_id desc;
+-----------+--------+-------------+
| course_id | cname | avg(number) |
+-----------+--------+-------------+
| 3 | 化学 | 58.0000 |
| 1 | 生物 | 60.0000 |
| 8 | 政治 | 64.5000 |
| 5 | 数学 | 65.5000 |
| 10 | python | 71.0000 |
| 9 | 历史 | 71.0000 |
| 4 | 体育 | 77.5000 |
| 6 | 语文 | 88.0000 |
| 2 | 物理 | 91.0000 |
| 7 | 英语 | 96.0000 |
+-----------+--------+-------------+
10 rows in set (0.00 sec)
-- 14.查询平均成绩大于85的所有学生的学号、姓名和平均成绩
mysql> select student_id , sname , avg(number) from student left join score
-> on student_id = student.sid
-> group by student_id , sname having avg(number) > 85;
+------------+-------+-------------+
| student_id | sname | avg(number) |
+------------+-------+-------------+
| 5 | 李四 | 91.5000 |
| 6 | 哪吒 | 88.5000 |
+------------+-------+-------------+
2 rows in set (0.00 sec)
-- 15.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；
mysql> select student_id , sname from student left join score on
-> student_id = student.sid
-> where course_id = 3 and number > 80;
Empty set (0.00 sec)
-- 16.查询各个课程及相应的选修人数
mysql> select cname ,count(student_id) from course left join score on
-> course_id = course.cid
-> group by cname;
+--------+-------------------+
| cname | count(student_id) |
+--------+-------------------+
| python | 1 |
| 体育 | 2 |
| 化学 | 1 |
| 历史 | 2 |
| 政治 | 2 |
| 数学 | 2 |
| 物理 | 3 |
| 生物 | 1 |
| 英语 | 1 |
| 语文 | 1 |
+--------+-------------------+
10 rows in set (0.00 sec)
-- 17.查询“4”课程分数小于60，按分数降序排列的同学学号
mysql> select student_id from score
-> where course_id = 4 and number < 60
-> order by student_id desc
-> ;
Empty set (0.00 sec)
-- 18.删除学号为“2”的同学的“1”课程的成绩
mysql> delete from score
-> where student_id = 2 and course_id = 1;
Query OK, 0 rows affected (0.00 sec)