day35

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.sname,sid from scores right join student on
-> sid=scores.student_id where scores.number1>60;
+----------+-----+
| sname | sid |
+----------+-----+
| xiaoning | 1 |
| xiaoming | 2 |
| xiaoa | 3 |
+----------+-----+
3 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 count(course_id),teacher_id from teacher_course group by teacher_id;
+------------------+------------+
| count(course_id) | teacher_id |
+------------------+------------+
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
+------------------+------------+
3 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 sname,sid ,caption from clas left join student on
-> class_id=clas.cid;
+----------+------+--------------+
| sname | sid | caption |
+----------+------+--------------+
| xiaoning | 1 | 三年二班 |
| xiaod | 5 | 三年二班 |
| xiaof | 7 | 三年二班 |
| xiaoming | 2 | 一年三班 |
| xiaoa | 3 | 一年三班 |
| xiaoe | 6 | 一年三班 |
| xiaob | 4 | 三年一班 |
| xiaog | 8 | 三年一班 |
+----------+------+--------------+
8 rows in set (0.00 sec)

-- 4、学生中男生的个数和女生的个数

mysql> select count(sid),gender from student group by gender;
+------------+--------+
| count(sid) | gender |
+------------+--------+
| 5 | 男 |
| 3 | 女 |
+------------+--------+
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_id,sname,number1 from scores left join student on sid=scores.student_id where scores.course_id=1;
+------------+----------+---------+
| student_id | sname | number1 |
+------------+----------+---------+
| 1 | xiaoning | 80 |
| 2 | xiaoming | 70 |
| 3 | xiaoa | 50 |
+------------+----------+---------+
3 rows 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_id ,avg(number1)as pj from scores group by student_id having pj > 60;
+------------+---------+
| student_id | pj |
+------------+---------+
| 1 | 66.6667 |
| 2 | 70.0000 |
| 3 | 70.0000 |
+------------+---------+
3 rows in set (0.00 sec)

-- 7、查询姓“张”的老师的个数；

mysql> select count(tid) from teacher where teacher.tname like '张%' group by tid;
+------------+
| count(tid) |
+------------+
| 1 |
+------------+
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 DISTINCT student.sname,sid from scores right join student on
-> sid=scores.student_id where scores.number1<60;
+----------+-----+
| sname | sid |
+----------+-----+
| xiaoning | 1 |
| xiaoa | 3 |
+----------+-----+
2 rows in set (0.00 sec)

-- 9. 删除学习“叶平”老师课的SC表记录

-- 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(number1),min(number1) from scores group by course_id;
+-----------+--------------+--------------+
| course_id | max(number1) | min(number1) |
+-----------+--------------+--------------+
| 1 | 80 | 50 |
| 2 | 70 | 40 |
| 3 | 90 | 80 |
+-----------+--------------+--------------+
3 rows in set (0.00 sec)mysql> select course_id ,max(number1),min(number1) from scores group by course_id;
+-----------+--------------+--------------+
| course_id | max(number1) | min(number1) |
+-----------+--------------+--------------+
| 1 | 80 | 50 |
| 2 | 70 | 40 |
| 3 | 90 | 80 |
+-----------+--------------+--------------+
3 rows in set (0.00 sec)

-- 11.查询每门课程被选修的学生数

mysql> select course_id,count(student_id) from scores group by course_id;
+-----------+-------------------+
| course_id | count(student_id) |
+-----------+-------------------+
| 1 | 3 |
| 2 | 3 |
| 3 | 3 |
+-----------+-------------------+
3 rows in set (0.00 sec)

-- 12.查询姓“xiao”的学生名单；

mysql> select * from student where sname like 'xiao%';
+-----+----------+--------+----------+
| sid | sname | gender | class_id |
+-----+----------+--------+----------+
| 1 | xiaoning | 男 | 1 |
| 2 | xiaoming | 男 | 2 |
| 3 | xiaoa | 男 | 2 |
| 4 | xiaob | 男 | 3 |
| 5 | xiaod | 女 | 1 |
| 6 | xiaoe | 女 | 2 |
| 7 | xiaof | 男 | 1 |
| 8 | xiaog | 女 | 3 |
+-----+----------+--------+----------+
8 rows 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,avg(number1)from scores group by course_id,
-> course_id order by avg(number1) asc,course_id desc;
+-----------+--------------+
| course_id | avg(number1) |
+-----------+--------------+
| 2 | 56.6667 |
| 1 | 66.6667 |
| 3 | 83.3333 |
+-----------+--------------+
3 rows in set (0.00 sec)

-- 14.查询平均成绩大于60的所有学生的学号、姓名和平均成绩

mysql> select student_id ,sname,avg(number1)as pj from scores left join
-> student on scores.student_id = student.sid group by student_id;
+------------+----------+---------+
| student_id | sname | pj |
+------------+----------+---------+
| 1 | xiaoning | 66.6667 |
| 2 | xiaoming | 70.0000 |
| 3 | xiaoa | 70.0000 |
+------------+----------+---------+
3 rows in set (0.00 sec)

-- 15.查询课程编号为3且课程成绩在65分以上的学生的学号和姓名；

mysql> select student_id ,sname from scores left join
-> student on scores.student_id = student.sid where course_id=3 and number1>65;
+------------+----------+
| student_id | sname |
+------------+----------+
| 1 | xiaoning |
| 2 | xiaoming |
| 3 | xiaoa |
+------------+----------+
3 rows in set (0.00 sec)

-- 16.查询各个课程及相应的选修人数

mysql> select cname,course_id,count(student_id) from scores left join course
-> on scores.course_id=course.coid group by course_id;
+--------+-----------+-------------------+
| cname | course_id | count(student_id) |
+--------+-----------+-------------------+
| 生物 | 1 | 3 |
| 物理 | 2 | 3 |
| 体育 | 3 | 3 |
+--------+-----------+-------------------+
3 rows in set (0.02 sec)

-- 17.查询“2”课程分数小于85，按分数降序排列的同学学号

mysql> select student_id from scores where number1<85 and course_id=2 order by number1 desc;
+------------+
| student_id |
+------------+
| 3 |
| 2 |
| 1 |
+------------+
3 rows in set (0.00 sec)

-- 18.删除学号为“2”的同学的“1”课程的成绩

mysql> delete from scores where student_id=2 and course_id=1;
Query OK, 1 row affected (0.07 sec)

mysql> select * from scores where student_id=2;
+------+------------+-----------+---------+
| scid | student_id | course_id | number1 |
+------+------------+-----------+---------+
| 5 | 2 | 2 | 60 |
| 8 | 2 | 3 | 80 |
+------+------------+-----------+---------+

-- 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.sname,sid from scores right join student on
    -> sid=scores.student_id where scores.number1>60;
+----------+-----+
| sname    | sid |
+----------+-----+
| xiaoning |   1 |
| xiaoming |   2 |
| xiaoa    |   3 |
+----------+-----+
3 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 count(course_id),teacher_id from teacher_course group by teacher_id;
+------------------+------------+
| count(course_id) | teacher_id |
+------------------+------------+
|                2 |          1 |
|                2 |          2 |
|                2 |          3 |
+------------------+------------+
3 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 sname,sid ,caption from clas left join student on
    -> class_id=clas.cid;
+----------+------+--------------+
| sname    | sid  | caption      |
+----------+------+--------------+
| xiaoning |    1 | 三年二班     |
| xiaod    |    5 | 三年二班     |
| xiaof    |    7 | 三年二班     |
| xiaoming |    2 | 一年三班     |
| xiaoa    |    3 | 一年三班     |
| xiaoe    |    6 | 一年三班     |
| xiaob    |    4 | 三年一班     |
| xiaog    |    8 | 三年一班     |
+----------+------+--------------+
8 rows in set (0.00 sec)

-- 4、学生中男生的个数和女生的个数

mysql> select count(sid),gender from student group by gender;
+------------+--------+
| count(sid) | gender |
+------------+--------+
|          5 | 男     |
|          3 | 女     |
+------------+--------+
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_id,sname,number1 from scores left join student on sid=scores.student_id where scores.course_id=1;
+------------+----------+---------+
| student_id | sname    | number1 |
+------------+----------+---------+
|          1 | xiaoning |      80 |
|          2 | xiaoming |      70 |
|          3 | xiaoa    |      50 |
+------------+----------+---------+
3 rows 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_id ,avg(number1)as pj from scores group by student_id having pj > 60;
+------------+---------+
| student_id | pj      |
+------------+---------+
|          1 | 66.6667 |
|          2 | 70.0000 |
|          3 | 70.0000 |
+------------+---------+
3 rows in set (0.00 sec)

-- 7、查询姓“张”的老师的个数；

mysql> select  count(tid) from teacher where teacher.tname like '张%' group by tid;
+------------+
| count(tid) |
+------------+
|          1 |
+------------+
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 DISTINCT student.sname,sid from scores right join student on
    -> sid=scores.student_id where scores.number1<60;
+----------+-----+
| sname    | sid |
+----------+-----+
| xiaoning |   1 |
| xiaoa    |   3 |
+----------+-----+
2 rows in set (0.00 sec)

-- 9. 删除学习“叶平”老师课的SC表记录



-- 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(number1),min(number1) from scores group by course_id;
+-----------+--------------+--------------+
| course_id | max(number1) | min(number1) |
+-----------+--------------+--------------+
|         1 |           80 |           50 |
|         2 |           70 |           40 |
|         3 |           90 |           80 |
+-----------+--------------+--------------+
3 rows in set (0.00 sec)mysql> select course_id ,max(number1),min(number1) from scores group by course_id;
+-----------+--------------+--------------+
| course_id | max(number1) | min(number1) |
+-----------+--------------+--------------+
|         1 |           80 |           50 |
|         2 |           70 |           40 |
|         3 |           90 |           80 |
+-----------+--------------+--------------+
3 rows in set (0.00 sec)

-- 11.查询每门课程被选修的学生数

mysql> select course_id,count(student_id) from scores group by course_id;
+-----------+-------------------+
| course_id | count(student_id) |
+-----------+-------------------+
|         1 |                 3 |
|         2 |                 3 |
|         3 |                 3 |
+-----------+-------------------+
3 rows in set (0.00 sec)

-- 12.查询姓“xiao”的学生名单；

mysql> select * from student where sname like 'xiao%';
+-----+----------+--------+----------+
| sid | sname    | gender | class_id |
+-----+----------+--------+----------+
|   1 | xiaoning | 男     |        1 |
|   2 | xiaoming | 男     |        2 |
|   3 | xiaoa    | 男     |        2 |
|   4 | xiaob    | 男     |        3 |
|   5 | xiaod    | 女     |        1 |
|   6 | xiaoe    | 女     |        2 |
|   7 | xiaof    | 男     |        1 |
|   8 | xiaog    | 女     |        3 |
+-----+----------+--------+----------+
8 rows 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,avg(number1)from scores group by course_id,
    -> course_id order by avg(number1) asc,course_id desc;
+-----------+--------------+
| course_id | avg(number1) |
+-----------+--------------+
|         2 |      56.6667 |
|         1 |      66.6667 |
|         3 |      83.3333 |
+-----------+--------------+
3 rows in set (0.00 sec)

-- 14.查询平均成绩大于60的所有学生的学号、姓名和平均成绩

mysql> select student_id ,sname,avg(number1)as pj from scores left join
    -> student on scores.student_id = student.sid group by student_id;
+------------+----------+---------+
| student_id | sname    | pj      |
+------------+----------+---------+
|          1 | xiaoning | 66.6667 |
|          2 | xiaoming | 70.0000 |
|          3 | xiaoa    | 70.0000 |
+------------+----------+---------+
3 rows in set (0.00 sec)

-- 15.查询课程编号为3且课程成绩在65分以上的学生的学号和姓名；

mysql> select student_id ,sname from scores left join
    -> student on scores.student_id = student.sid where course_id=3 and number1>65;
+------------+----------+
| student_id | sname    |
+------------+----------+
|          1 | xiaoning |
|          2 | xiaoming |
|          3 | xiaoa    |
+------------+----------+
3 rows in set (0.00 sec)

-- 16.查询各个课程及相应的选修人数

mysql>  select cname,course_id,count(student_id) from scores left join course
    ->  on scores.course_id=course.coid group by course_id;
+--------+-----------+-------------------+
| cname  | course_id | count(student_id) |
+--------+-----------+-------------------+
| 生物   |         1 |                 3 |
| 物理   |         2 |                 3 |
| 体育   |         3 |                 3 |
+--------+-----------+-------------------+
3 rows in set (0.02 sec)

-- 17.查询“2”课程分数小于85，按分数降序排列的同学学号

mysql> select student_id from scores where number1<85 and course_id=2 order by number1 desc;
+------------+
| student_id |
+------------+
|          3 |
|          2 |
|          1 |
+------------+
3 rows in set (0.00 sec)

-- 18.删除学号为“2”的同学的“1”课程的成绩

mysql> delete from scores where student_id=2 and course_id=1;
Query OK, 1 row affected (0.07 sec)

mysql> select * from scores where student_id=2;
+------+------------+-----------+---------+
| scid | student_id | course_id | number1 |
+------+------------+-----------+---------+
|    5 |          2 |         2 |      60 |
|    8 |          2 |         3 |      80 |
+------+------------+-----------+---------+