-查询姓“猴”的学生名单
-查询姓名中最后一个字是“猴”的学生名单
-查询姓名中带“猴”的学生名单
select * from student where 姓名 like '猴%';
select * from student where 姓名 like '%猴';
select * from student where 姓名 like '%猴%'; 

select count(教师号) from teacher where 教师姓名 like '孟%'; 

select sum(成绩)
from score
where 课程号 = '0002';

select count(distinct 学号) as 学生人数
from score;

select 课程号,max(成绩) as 最高分,min(成绩) as 最低分
from score
group by 课程号;

select 课程号, count(学号)
from score
group by 课程号;

select 性别,count(*)
from student
group by 性别;

select 学号, avg(成绩)
from score
group by 学号
having avg(成绩)>60;

select 学号, count(课程号) as 选修课程数目
from score
group by 学号
having count(课程号)>=2;

select 姓名,count(*) as 人数
from student
group by 姓名
having count(*)>=2;

select 课程号
from score
where 成绩<60
order by 课程号 desc;

select 课程号, avg(成绩) as 平均成绩
from score
group by 课程号
order by 平均成绩,课程号 desc;

select 学号
from score
where 课程号='0004' and 成绩<60
order by 成绩 desc;

select 课程号,count(学生号) as 选修人数
from score
group by 课程号
having count(学生号)>2
order by 选修人数 desc,课程号;

select 学号,avg(成绩) as 平均成绩
from score
where 成绩<60
group by 学号
having count(课程号)>2;

select distinct a.学号,a.学生姓名
from student a join score b
on a.学号=b.学号
where 成绩<60;
或者：
select 学号,姓名
from student
where 学号 in (
select 学号
from score
group by 学号
having max(成绩)<60
);

/*
查找出学号，条件：没有学全所有课，也就是该学生选修的课程数<总的课程数
【考察知识点】in，两个子查询的比较
*/
select 学号,姓名
from student
where 学号 in(
select 学号
from score
group by 学号
having count(课程号)<(select count(课程号) from course)
);

select 学号,姓名
from student
where 学号 in(
select 学号
from score
group by 学号
having count(课程号)=2);

/*查找1990年出生的学生名单，由于学生表中出生日期列的类型是datetime 所以用year函数获取年份*/
select 学号,姓名
from student
where year(出生日期)=1990;

select *
from score as a
where 成绩 in(
select max(成绩)
from score as b
where a.课程号=b.课程号
group by 课程号);

select *
from score as a
where 成绩 in(
select min(成绩)
from score as b
where b.课程号 = a.课程号
group by 课程号);

(select * from score where 课程号 = '0001' order by 成绩 desc limit 2)
union all
(select * from score where 课程号 = '0002' order by 成绩 desc limit 2)
union all
(select * from score where 课程号 = '0003' order by 成绩 desc limit 2);

select a.姓名 as 不近视的学生
from 学生表 as a left join 近视学生表 as b on a.学号=b.学生学号 where b.序号 is null;

select a.学号,a.姓名,count(b.课程号) as 选课数,sum(b.成绩) as 总成绩
from student as a left join score as b
on a.学号 = b.学号
group by a.学号;

select a.学号,a.姓名, avg(b.成绩) as 平均成绩
from student as a left join score as b
on a.学号 = b.学号
group by a.学号
having avg(b.成绩)›85;

select a.学号, a.姓名, c.课程号,c.课程名称
from student a inner join score b on a.学号=b.学号
inner join course c on b.课程号=c.课程号;

select 课程号,
sum(case when 成绩>=60 then 1 else 0 end) as 及格人数,
sum(case when 成绩<60 then 1 else 0 end) as 不及格人数
from score
group by 课程号;

select a.课程号,b.课程名称,
sum(case when 成绩 between 85 and 100 then 1 else 0 end) as '[100-85]',
sum(case when 成绩>=70 and 成绩<85 then 1 else 0 end) as '[85-70]',
sum(case when 成绩>=60 and 成绩<70 then 1 else 0 end) as '[70-60]',
sum(case when 成绩<60 then 1 else 0 end) as '[<60]'
from score as a right join course as b
on a.课程号=b.课程号
group by a.课程号,b.课程名称;

select a.学号,a.姓名
from student  as a inner join score as b on a.学号=b.学号
where b.课程号='0003' and b.成绩>80;

select 学号,
max(case when 课程号='0001' then 成绩 else 0 end) as '课程号0001',
max(case when 课程号='0002' then 成绩 else 0 end) as '课程号0002',
max(case when 课程号='0003' then 成绩 else 0 end) as '课程号0003'
from score
group by 学号;