数据表介绍
--1.学生表
Student(SId,Sname,Sage,Ssex)
--SId 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
--2.课程表
Course(CId,Cname,TId)
--CId 课程编号,Cname 课程名称,TId 教师编号
--3.教师表
Teacher(TId,Tname)
--TId 教师编号,Tname 教师姓名
--4.成绩表
SC(SId,CId,score)
--SId 学生编号,CId 课程编号,score 分数
学生表 Student
create table Student(SId varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10));
insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into Student values('02' , '钱电' , '1990-12-21' , '男');
insert into Student values('03' , '孙风' , '1990-12-20' , '男');
insert into Student values('04' , '李云' , '1990-12-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-01-01' , '女');
insert into Student values('07' , '郑竹' , '1989-01-01' , '女');
insert into Student values('09' , '张三' , '2017-12-20' , '女');
insert into Student values('10' , '李四' , '2017-12-25' , '女');
insert into Student values('11' , '李四' , '2012-06-06' , '女');
insert into Student values('12' , '赵六' , '2013-06-13' , '女');
insert into Student values('13' , '孙七' , '2014-06-01' , '女');
科目表 Course
create table Course(CId varchar(10),Cname nvarchar(10),TId varchar(10));
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
教师表 Teacher
create table Teacher(TId varchar(10),Tname varchar(10));
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');
成绩表 SC
create table SC(SId varchar(10),CId varchar(10),score decimal(18,1));
insert into SC values('01' , '01' , 80);
insert into SC values('01' , '02' , 90);
insert into SC values('01' , '03' , 99);
insert into SC values('02' , '01' , 70);
insert into SC values('02' , '02' , 60);
insert into SC values('02' , '03' , 80);
insert into SC values('03' , '01' , 80);
insert into SC values('03' , '02' , 80);
insert into SC values('03' , '03' , 80);
insert into SC values('04' , '01' , 50);
insert into SC values('04' , '02' , 30);
insert into SC values('04' , '03' , 20);
insert into SC values('05' , '01' , 76);
insert into SC values('05' , '02' , 87);
insert into SC values('06' , '01' , 31);
insert into SC values('06' , '03' , 34);
insert into SC values('07' , '02' , 89);
insert into SC values('07' , '03' , 98);
1.查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
select SId,CId,score from sc where CId=1; //查出01课程的学生，作为b1
select SId,CId,score from sc where CId=2; //b2
select distinct b1.SId,b1.score from (select SId,CId,score from sc where CId=1) b1, (select SId,CId,score from sc where CId=2) b2 where b1.score>b2.score; //查出01课程分数比02课程高的人，b3
mysql> select st.*,b3.score from student st inner join (select distinct b1.SId,b1.score from (select SId,CId,score from sc where CId=1) b1, (select SId,CId,score from sc where CId=2) b2 where b1.score>b2.score) b3 on(st.SId=b3.SId);
+------+--------+---------------------+------+-------+
| SId | Sname | Sage | Ssex | score |
+------+--------+---------------------+------+-------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 | 80.0 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 | 70.0 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 | 80.0 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 | 50.0 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 | 76.0 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 | 31.0 |
+------+--------+---------------------+------+-------+
6 rows in set (0.01 sec) //将b3查出的表和student表关联查询得出学生的信息
2.查询同时存在" 01 "课程和" 02 "课程的情况
select * from sc where CId=1; //查询课程1
select * from sc where CId=2; //查询课程2
mysql> select * from (select * from sc where CId=1) b1,(select * from sc where CId=2) b2 where b1.SId=b2.SId;
+------+------+-------+------+------+-------+
| SId | CId | score | SId | CId | score |
+------+------+-------+------+------+-------+
| 01 | 01 | 80.0 | 01 | 02 | 90.0 |
| 02 | 01 | 70.0 | 02 | 02 | 60.0 |
| 03 | 01 | 80.0 | 03 | 02 | 80.0 |
| 04 | 01 | 50.0 | 04 | 02 | 30.0 |
| 05 | 01 | 76.0 | 05 | 02 | 87.0 |
+------+------+-------+------+------+-------+
5 rows in set (0.01 sec)
//联合两张表，查询课程1，2都有的人
3.查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )
mysql> select * from (select * from sc where CId=1) b1 left join (select * from sc where CId=2) b2 on(b1.SId=b2.SId);
+------+------+-------+------+------+-------+
| SId | CId | score | SId | CId | score |
+------+------+-------+------+------+-------+
| 01 | 01 | 80.0 | 01 | 02 | 90.0 |
| 02 | 01 | 70.0 | 02 | 02 | 60.0 |
| 03 | 01 | 80.0 | 03 | 02 | 80.0 |
| 04 | 01 | 50.0 | 04 | 02 | 30.0 |
| 05 | 01 | 76.0 | 05 | 02 | 87.0 |
| 06 | 01 | 31.0 | NULL | NULL | NULL |
+------+------+-------+------+------+-------+
6 rows in set (0.00 sec)
4.查询不存在" 01 "课程但存在" 02 "课程的情况
mysql> select * from sc where SId not in(select SId from sc where sc.CId=1) and sc.CId=2;
+------+------+-------+
| SId | CId | score |
+------+------+-------+
| 07 | 02 | 89.0 |
+------+------+-------+
1 row in set (0.00 sec)
5.查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩
mysql> select st.sid,st.sname,b1.avg
-> from student st,(select SId,avg(score) avg from sc group by SId having avg(score)>60) b1
-> where st.sid=b1.sid;
+------+--------+----------+
| sid | sname | avg |
+------+--------+----------+
| 01 | 赵雷 | 89.66667 |
| 02 | 钱电 | 70.00000 |
| 03 | 孙风 | 80.00000 |
| 05 | 周梅 | 81.50000 |
| 07 | 郑竹 | 93.50000 |
+------+--------+----------+
5 rows in set (0.00 sec)
6.查询在 SC 表存在成绩的学生信息
mysql> select distinct st.* from student st,sc where st.sid=sc.sid;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
7 rows in set (0.00 sec)
7.查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )
mysql> select st.sid,st.sname,b1.选课数,b1.总成绩
-> from (select student.sid,student.sname from student) st
-> left join (select sid,count(sid) 选课数,sum(score) 总成绩 from sc group by sid) b1
-> on(st.sid=b1.sid);
+------+--------+-----------+-----------+
| sid | sname | 选课数 | 总成绩 |
+------+--------+-----------+-----------+
| 01 | 赵雷 | 3 | 269.0 |
| 02 | 钱电 | 3 | 210.0 |
| 03 | 孙风 | 3 | 240.0 |
| 04 | 李云 | 3 | 100.0 |
| 05 | 周梅 | 2 | 163.0 |
| 06 | 吴兰 | 2 | 65.0 |
| 07 | 郑竹 | 2 | 187.0 |
| 09 | 张三 | NULL | NULL |
| 10 | 李四 | NULL | NULL |
| 11 | 李四 | NULL | NULL |
| 12 | 赵六 | NULL | NULL |
| 13 | 孙七 | NULL | NULL |
+------+--------+-----------+-----------+
12 rows in set (0.00 sec)
8.查有成绩的学生信息
mysql> select * from student where student.sid in (select sc.sid from sc);
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
7 rows in set (0.00 sec)
9.查询「李」姓老师的数量
mysql> select count(tname) from teacher where tname like '李%';
+--------------+
| count(tname) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)
10.查询学过「张三」老师授课的同学的信息
mysql> select st.* from student st,
-> (select sc.sid
-> from sc,(select CId from course where tid=(select tid from teacher where tname='张三')) b1
-> where sc.cid=b1.cid) b2
-> where st.sid=b2.sid;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
6 rows in set (0.00 sec)
11.查询没有学全所有课程的同学的信息
mysql> select st.* from student st
-> where st.sid not in
-> (select sc.sid
-> from sc group by sc.sid
-> having count(sc.cid)=(select count(cid) from course));
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
| 09 | 张三 | 2017-12-20 00:00:00 | 女 |
| 10 | 李四 | 2017-12-25 00:00:00 | 女 |
| 11 | 李四 | 2012-06-06 00:00:00 | 女 |
| 12 | 赵六 | 2013-06-13 00:00:00 | 女 |
| 13 | 孙七 | 2014-06-01 00:00:00 | 女 |
+------+--------+---------------------+------+
8 rows in set (0.00 sec)
12.查询至少有一门课与学号为" 01 "的同学所学相同的同学的信息
mysql> select st.* from
-> student st,
-> (select distinct sid from sc where sc.cid in((select cid from sc where sid=1))) b1
-> where st.sid=b1.sid;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
7 rows in set (0.00 sec)
13.查询和" 01 "号的同学学习的课程 完全相同的其他同学的信息
mysql> select st.* from student st,
-> (select sid from
-> (select count(cid) 选课数 from sc where sid=1) b1,
-> (select sid,count(cid) 选课数 from sc group by sid) b2
-> where b1.选课数=b2.选课数) b3
-> where st.sid=b3.sid;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
+------+--------+---------------------+------+
4 rows in set (0.00 sec)
14.查询没学过"张三"老师讲授的任一门课程的学生姓名
mysql> select * from student where student.sid not
-> in(select sc.sid from sc where sc.cid
-> in(select cid from course co,
-> (select tid from teacher where tname='张三') b1
-> where co.tid=b1.tid));
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 09 | 张三 | 2017-12-20 00:00:00 | 女 |
| 10 | 李四 | 2017-12-25 00:00:00 | 女 |
| 11 | 李四 | 2012-06-06 00:00:00 | 女 |
| 12 | 赵六 | 2013-06-13 00:00:00 | 女 |
| 13 | 孙七 | 2014-06-01 00:00:00 | 女 |
+------+--------+---------------------+------+
6 rows in set (0.00 sec)
15.查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩
mysql> select st.sid,st.sname,b1.avg from
-> student st,
-> (select sid,avg(score) avg from sc where score<60 group by sid having count(score)>1) b1
-> where st.sid=b1.sid;
+------+--------+----------+
| sid | sname | avg |
+------+--------+----------+
| 04 | 李云 | 33.33333 |
| 06 | 吴兰 | 32.50000 |
+------+--------+----------+
2 rows in set (0.00 sec)
16.检索" 01 "课程分数小于 60，按分数降序排列的学生信息
mysql> select st.*,b1.score from student st,
-> (select sid,score from sc where cid=1 and score<60) b1
-> where st.sid=b1.sid
-> order by b1.score desc;
+------+--------+---------------------+------+-------+
| SId | Sname | Sage | Ssex | score |
+------+--------+---------------------+------+-------+
| 04 | 李云 | 1990-12-06 00:00:00 | 男 | 50.0 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 | 31.0 |
+------+--------+---------------------+------+-------+
2 rows in set (0.00 sec)
17.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩
mysql> select sc.sid,sc.cid,b1.avg from sc
-> left join
-> (select sid,avg(score) avg from sc group by sid) b1
-> on sc.sid=b1.sid
-> order by avg desc;
+------+------+----------+
| sid | cid | avg |
+------+------+----------+
| 07 | 02 | 93.50000 |
| 07 | 03 | 93.50000 |
| 01 | 01 | 89.66667 |
| 01 | 02 | 89.66667 |
| 01 | 03 | 89.66667 |
| 05 | 01 | 81.50000 |
| 05 | 02 | 81.50000 |
| 03 | 01 | 80.00000 |
| 03 | 02 | 80.00000 |
| 03 | 03 | 80.00000 |
| 02 | 01 | 70.00000 |
| 02 | 02 | 70.00000 |
| 02 | 03 | 70.00000 |
| 04 | 01 | 33.33333 |
| 04 | 02 | 33.33333 |
| 04 | 03 | 33.33333 |
| 06 | 01 | 32.50000 |
| 06 | 03 | 32.50000 |
+------+------+----------+
18 rows in set (0.00 sec)
18.查询各科成绩最高分、最低分和平均分：以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率，及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90，要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列
mysql> select sc.cid,
-> max(sc.score) 最高分,
-> min(sc.score) 最低分,
-> avg(sc.score) 平均分,
-> count(*) 参选人数,
-> sum(case when sc.score>=60 then 1 else 0 end)/count(*) 及格率,
-> sum(case when sc.score>=70 and sc.score<80 then 1 else 0 end)/count(*) 中等率,
-> sum(case when sc.score>=80 and sc.score<90 then 1 else 0 end)/count(*) 优良率,
-> sum(case when sc.score>=90 then 1 else 0 end)/count(*) 优秀率
-> from sc
-> group by sc.cid
-> order by count(*) desc,sc.cid asc;
+------+-----------+-----------+-----------+--------------+-----------+-----------+-----------+-----------+
| cid | 最高分 | 最低分 | 平均分 | 参选人数 | 及格率 | 中等率 | 优良率 | 优秀率 |
+------+-----------+-----------+-----------+--------------+-----------+-----------+-----------+-----------+
| 01 | 80.0 | 31.0 | 64.50000 | 6 | 0.6667 | 0.3333 | 0.3333 | 0.0000 |
| 02 | 90.0 | 30.0 | 72.66667 | 6 | 0.8333 | 0.0000 | 0.5000 | 0.1667 |
| 03 | 99.0 | 20.0 | 68.50000 | 6 | 0.6667 | 0.0000 | 0.3333 | 0.3333 |
+------+-----------+-----------+-----------+--------------+-----------+-----------+-----------+-----------+
3 rows in set (0.00 sec)
19.按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺
mysql> select a.cid, a.sid, a.score, count(b.score)+1 an
-> from sc as a
-> left join sc as b
-> on a.score
-> order by a.cid, an aSC;
+------+------+-------+----+
| cid | sid | score | an |
+------+------+-------+----+
| 01 | 01 | 80.0 | 1 |
| 01 | 03 | 80.0 | 1 |
| 01 | 05 | 76.0 | 3 |
| 01 | 02 | 70.0 | 4 |
| 01 | 04 | 50.0 | 5 |
| 01 | 06 | 31.0 | 6 |
| 02 | 01 | 90.0 | 1 |
| 02 | 07 | 89.0 | 2 |
| 02 | 05 | 87.0 | 3 |
| 02 | 03 | 80.0 | 4 |
| 02 | 02 | 60.0 | 5 |
| 02 | 04 | 30.0 | 6 |
| 03 | 01 | 99.0 | 1 |
| 03 | 07 | 98.0 | 2 |
| 03 | 02 | 80.0 | 3 |
| 03 | 03 | 80.0 | 3 |
| 03 | 06 | 34.0 | 5 |
| 03 | 04 | 20.0 | 6 |
+------+------+-------+----+
18 rows in set (0.00 sec)
22. 查询学生的总成绩，并进行排名，总分重复时不保留名次空缺
mysql> select a.sid,total,@crank:=@crank+1 an from(
-> select sc.sid, sum(sc.score) total from sc
-> group by sc.sid order by total desc) a;
+------+-------+------+
| sid | total | an |
+------+-------+------+
| 01 | 269.0 | 1 |
| 03 | 240.0 | 2 |
| 02 | 210.0 | 3 |
| 07 | 187.0 | 4 |
| 05 | 163.0 | 5 |
| 04 | 100.0 | 6 |
| 06 | 65.0 | 7 |
+------+-------+------+
7 rows in set, 1 warning (0.00 sec)
23.统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比
24.查询各科成绩前三名的记录
mysql> select * from sc
-> where (
-> select count(*) from sc as a
-> where sc.cid = a.cid and sc.score
-> order by cid asc, sc.score desc;
+------+------+-------+
| SId | CId | score |
+------+------+-------+
| 01 | 01 | 80.0 |
| 03 | 01 | 80.0 |
| 05 | 01 | 76.0 |
| 01 | 02 | 90.0 |
| 07 | 02 | 89.0 |
| 05 | 02 | 87.0 |
| 01 | 03 | 99.0 |
| 07 | 03 | 98.0 |
| 02 | 03 | 80.0 |
| 03 | 03 | 80.0 |
+------+------+-------+
25.查询每门课程被选修的学生数
mysql> select cid,count(sid) from sc group by cid;
+------+------------+
| cid | count(sid) |
+------+------------+
| 01 | 6 |
| 02 | 6 |
| 03 | 6 |
+------+------------+
3 rows in set (0.00 sec)
26.查询出只选修两门课程的学生学号和姓名
mysql> select distinct st.sid,st.sname from student st inner join
-> (select sid,count(cid) 选课数 from sc group by sid having 选课数=2) b1
-> on(st.sid=b1.sid);
+------+--------+
| sid | sname |
+------+--------+
| 05 | 周梅 |
| 06 | 吴兰 |
| 07 | 郑竹 |
+------+--------+
3 rows in set (0.00 sec)
27.查询男生、女生人数
mysql> select ssex,count(*) from student group by ssex;
+------+----------+
| ssex | count(*) |
+------+----------+
| 男 | 4 |
| 女 | 8 |
+------+----------+
2 rows in set (0.00 sec)
28.查询名字中含有「风」字的学生信息
mysql> select * from student where sname like '%风%';
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
+------+--------+---------------------+------+
1 row in set (0.00 sec)
29.查询同名同性学生名单，并统计同名人数
mysql> select sname,count(*) from student group by sname having count(*)>1;
+--------+----------+
| sname | count(*) |
+--------+----------+
| 李四 | 2 |
+--------+----------+
1 row in set (0.00 sec)
30.查询 1990 年出生的学生名单
mysql> select * from student where year(sage)=1990;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
+------+--------+---------------------+------+
4 rows in set (0.01 sec)
31.查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列
mysql> select cid,avg(score) averg from sc group by cid order by averg desc;
+------+----------+
| cid | averg |
+------+----------+
| 02 | 72.66667 |
| 03 | 68.50000 |
| 01 | 64.50000 |
+------+----------+
3 rows in set (0.00 sec)
32.查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩
mysql> select st.sid,st.sname,b1.averg from student st inner join
-> (select sid,avg(score) averg from sc group by sid having averg>85) b1
-> on(st.sid=b1.sid);
+------+--------+----------+
| sid | sname | averg |
+------+--------+----------+
| 01 | 赵雷 | 89.66667 |
| 07 | 郑竹 | 93.50000 |
+------+--------+----------+
2 rows in set (0.00 sec)
33.查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
mysql> select st.sname,b2.score
-> from student st,
-> (select sid,score from
-> sc,(select cid from course where cname='数学') b1
-> where sc.cid=b1.cid and score<60) b2
-> where st.sid=b2.sid;
+--------+-------+
| sname | score |
+--------+-------+
| 李云 | 30.0 |
+--------+-------+
1 row in set (0.00 sec)
34.查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）
mysql> select st.sname,cid,score from student st
-> left join sc on st.sid=sc.sid;
+--------+------+-------+
| sname | cid | score |
+--------+------+-------+
| 赵雷 | 03 | 99.0 |
| 赵雷 | 02 | 90.0 |
| 赵雷 | 01 | 80.0 |
| 钱电 | 03 | 80.0 |
| 钱电 | 02 | 60.0 |
| 钱电 | 01 | 70.0 |
| 孙风 | 03 | 80.0 |
| 孙风 | 02 | 80.0 |
| 孙风 | 01 | 80.0 |
| 李云 | 03 | 20.0 |
| 李云 | 02 | 30.0 |
| 李云 | 01 | 50.0 |
| 周梅 | 02 | 87.0 |
| 周梅 | 01 | 76.0 |
| 吴兰 | 03 | 34.0 |
| 吴兰 | 01 | 31.0 |
| 郑竹 | 03 | 98.0 |
| 郑竹 | 02 | 89.0 |
| 张三 | NULL | NULL |
| 李四 | NULL | NULL |
| 李四 | NULL | NULL |
| 赵六 | NULL | NULL |
| 孙七 | NULL | NULL |
+--------+------+-------+
23 rows in set (0.00 sec)
35.查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数
mysql> select st.sname,c.cname,s.score from student st,course c,sc s
-> where s.score>70
-> and st.sid=s.sid
-> and s.cid=c.cid;
+--------+--------+-------+
| sname | cname | score |
+--------+--------+-------+
| 赵雷 | 英语 | 99.0 |
| 赵雷 | 数学 | 90.0 |
| 赵雷 | 语文 | 80.0 |
| 钱电 | 英语 | 80.0 |
| 孙风 | 英语 | 80.0 |
| 孙风 | 数学 | 80.0 |
| 孙风 | 语文 | 80.0 |
| 周梅 | 数学 | 87.0 |
| 周梅 | 语文 | 76.0 |
| 郑竹 | 英语 | 98.0 |
| 郑竹 | 数学 | 89.0 |
+--------+--------+-------+
11 rows in set (0.00 sec)
36.查询不及格的课程
mysql> select cid from sc where score<60 group by cid;
+------+
| cid |
+------+
| 01 |
| 02 |
| 03 |
+------+
3 rows in set (0.00 sec)
37.查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名
mysql> select distinct st.sid,st.sname from student st,sc
-> where sc.cid=1 and sc.score>=80 and st.sid=sc.sid;
+------+--------+
| sid | sname |
+------+--------+
| 01 | 赵雷 |
| 03 | 孙风 |
+------+--------+
2 rows in set (0.00 sec)
38.求每门课程的学生人数
mysql> select cid,count(sid) from sc group by cid;
+------+------------+
| cid | count(sid) |
+------+------------+
| 01 | 6 |
| 02 | 6 |
| 03 | 6 |
+------+------------+
3 rows in set (0.00 sec)
39.成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩
mysql> select student.*, sc.score, sc.cid from student, teacher, course,sc
-> where teacher.tid = course.tid
-> and sc.sid = student.sid
-> and sc.cid = course.cid
-> and teacher.tname = "张三"
-> order by score desc
-> limit 1;
+------+--------+---------------------+------+-------+------+
| SId | Sname | Sage | Ssex | score | cid |
+------+--------+---------------------+------+-------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 | 90.0 | 02 |
+------+--------+---------------------+------+-------+------+
1 row in set (0.00 sec)
41.查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩
mysql> select distinct a.cid, a.sid, a.score from sc as a
-> inner join
-> sc as b
-> on a.sid = b.sid
-> and a.cid != b.cid
-> and a.score = b.score;
+------+------+-------+
| cid | sid | score |
+------+------+-------+
| 03 | 03 | 80.0 |
| 02 | 03 | 80.0 |
| 01 | 03 | 80.0 |
+------+------+-------+
3 rows in set (0.01 sec)
42.查询每门功成绩最好的前两名
43.统计每门课程的学生选修人数（超过 5 人的课程才统计）。
mysql> select cid,count(sid) from sc group by cid having count(sid)>5;
+------+------------+
| cid | count(sid) |
+------+------------+
| 01 | 6 |
| 02 | 6 |
| 03 | 6 |
+------+------------+
3 rows in set (0.00 sec)
44.检索至少选修两门课程的学生学号
mysql> select sid,count(cid) s from sc group by sid having s>-2;
+------+---+
| sid | s |
+------+---+
| 01 | 3 |
| 02 | 3 |
| 03 | 3 |
| 04 | 3 |
| 05 | 2 |
| 06 | 2 |
| 07 | 2 |
+------+---+
7 rows in set (0.00 sec)
45.查询选修了全部课程的学生信息
mysql> select st.* from student st,
-> (select sid from sc group by sid having count(cid)=(select count(*) from course)) b1
-> where st.sid=b1.sid;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
+------+--------+---------------------+------+
4 rows in set (0.00 sec)
46.查询各学生的年龄，只按年份来算
mysql> select sname,year(curdate())-year(sage) 年龄 from student;
+--------+--------+
| sname | 年龄 |
+--------+--------+
| 赵雷 | 33 |
| 钱电 | 33 |
| 孙风 | 33 |
| 李云 | 33 |
| 周梅 | 32 |
| 吴兰 | 31 |
| 郑竹 | 34 |
| 张三 | 6 |
| 李四 | 6 |
| 李四 | 11 |
| 赵六 | 10 |
| 孙七 | 9 |
+--------+--------+
12 rows in set (0.01 sec)
47.按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一
mysql> select student.SId as 学生编号,student.Sname as 学生姓名,
-> TIMESTAMPDIFF(YEAR,student.Sage,CURDATE()) as 学生年龄
-> from student
-> ;
+--------------+--------------+--------------+
| 学生编号 | 学生姓名 | 学生年龄 |
+--------------+--------------+--------------+
| 01 | 赵雷 | 33 |
| 02 | 钱电 | 32 |
| 03 | 孙风 | 32 |
| 04 | 李云 | 32 |
| 05 | 周梅 | 31 |
| 06 | 吴兰 | 31 |
| 07 | 郑竹 | 34 |
| 09 | 张三 | 5 |
| 10 | 李四 | 5 |
| 11 | 李四 | 11 |
| 12 | 赵六 | 10 |
| 13 | 孙七 | 9 |
+--------------+--------------+--------------+
12 rows in set (0.01 sec)
48.查询本周过生日的学生
mysql> select *
-> from student
-> where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE());
Empty set (0.00 sec)
49.查询下周过生日的学生
mysql> select *
-> from student
-> where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE())+1;
Empty set (0.00 sec)
50.查询本月过生日的学生
mysql> select *
-> from student
-> where MONTH(student.Sage)=MONTH(CURDATE());
Empty set (0.01 sec)
51查询下月过生日的学生
mysql> select *
-> from student
-> where MONTH(student.Sage)=MONTH(CURDATE())+1;
Empty set (0.00 sec)