- 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 | Ů |
+------------+--------+
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 | Ů | 1 |
| 6 | xiaoe | Ů | 2 |
| 7 | xiaof | 男 | 1 |
| 8 | xiaog | Ů | 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 | +------+------------+-----------+---------+
来源：博客园
作者：ylpb
链接：https://www.cnblogs.com/ghylpb/p/11769002.html