CREATE TABLE `Student`(

`s_id` VARCHAR(20),

`s_name` VARCHAR(20) NOT NULL DEFAULT '',

`s_birth` VARCHAR(20) NOT NULL DEFAULT '',

`s_sex` VARCHAR(10) NOT NULL DEFAULT '',

PRIMARY KEY(`s_id`)

);

CREATE TABLE `Course`(

`c_id` VARCHAR(20),

`c_name` VARCHAR(20) NOT NULL DEFAULT '',

`t_id` VARCHAR(20) NOT NULL,

PRIMARY KEY(`c_id`)

);

CREATE TABLE `Teacher`(

`t_id` VARCHAR(20),

`t_name` VARCHAR(20) NOT NULL DEFAULT '',

PRIMARY KEY(`t_id`)

);

CREATE TABLE `Score`(

`s_id` VARCHAR(20),

`c_id` VARCHAR(20),

`s_score` INT(3),

PRIMARY KEY(`s_id`,`c_id`)

);

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' , '1990-05-20' , '男');

insert into Student values('04' , '李云' , '1990-08-06' , '男');

insert into Student values('05' , '周梅' , '1991-12-01' , '女');

insert into Student values('06' , '吴兰' , '1992-03-01' , '女');

insert into Student values('07' , '郑竹' , '1989-07-01' , '女');

insert into Student values('08' , '王菊' , '1990-01-20' , '女');

insert into Course values('01' , '语文' , '02');

insert into Course values('02' , '数学' , '01');

insert into Course values('03' , '英语' , '03');

insert into Teacher values('01' , '张三');

insert into Teacher values('02' , '李四');

insert into Teacher values('03' , '王五');

insert into Score values('01' , '01' , 80);

insert into Score values('01' , '02' , 90);

insert into Score values('01' , '03' , 99);

insert into Score values('02' , '01' , 70);

insert into Score values('02' , '02' , 60);

insert into Score values('02' , '03' , 80);

insert into Score values('03' , '01' , 80);

insert into Score values('03' , '02' , 80);

insert into Score values('03' , '03' , 80);

insert into Score values('04' , '01' , 50);

insert into Score values('04' , '02' , 30);

insert into Score values('04' , '03' , 20);

insert into Score values('05' , '01' , 76);

insert into Score values('05' , '02' , 87);

insert into Score values('06' , '01' , 31);

insert into Score values('06' , '03' , 34);

insert into Score values('07' , '02' , 89);

insert into Score values('07' , '03' , 98);

select a.* ,b.s_score as 01_score,c.s_score as 02_score from

student a

join score b on a.s_id=b.s_id and b.c_id='01'

left join score c on a.s_id=c.s_id and c.c_id='02' or c.c_id = NULL where b.s_score>c.s_score

select a.* ,b.s_score as 01_score,c.s_score as 02_score from

student a left join score b on a.s_id=b.s_id and b.c_id='01' or b.c_id=NULL

join score c on a.s_id=c.s_id and c.c_id='02' where b.s_score<c.s_score

select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from

student b

join score a on b.s_id = a.s_id

GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)>=60;

-- (包括有成绩的和无成绩的)

select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from

student b

left join score a on b.s_id = a.s_id

GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)<60

union

select a.s_id,a.s_name,0 as avg_score from

student a

where a.s_id not in (

select distinct s_id from score);

select a.s_id,a.s_name,count(b.c_id) as sum_course,sum(b.s_score) as sum_score from

student a

left join score b on a.s_id=b.s_id

GROUP BY a.s_id,a.s_name;

select count(t_id) from teacher where t_name like '李%';

select a.* from

student a

join score b on a.s_id=b.s_id where b.c_id in(

select c_id from course where t_id =(

select t_id from teacher where t_name = '张三'));

select * from

student c

where c.s_id not in(

select a.s_id from student a join score b on a.s_id=b.s_id where b.c_id in(

select c_id from course where t_id =(

select t_id from teacher where t_name = '张三')));

select a.* from

student a,score b,score c

where a.s_id = b.s_id and a.s_id = c.s_id and b.c_id='01' and c.c_id='02';

select a.* from

student a

where a.s_id in (select s_id from score where c_id='01' ) and a.s_id not in(select s_id from score where c_id='02')

select s.* from

student s where s.s_id in(

select s_id from score where s_id not in(

select a.s_id from score a

join score b on a.s_id = b.s_id and b.c_id='02'

join score c on a.s_id = c.s_id and c.c_id='03'

where a.c_id='01'))

select * from student where s_id in(

select distinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.s_id='01')

);

select a.* from student a where a.s_id in(

select distinct s_id from score where s_id!='01' and c_id in(select c_id from score where s_id='01')

group by s_id

having count(1)=(select count(1) from score where s_id='01'));

select a.s_name from student a where a.s_id not in (

select s_id from score where c_id =

(select c_id from course where t_id =(

select t_id from teacher where t_name = '张三'))

group by s_id);

select a.s_id,a.s_name,ROUND(AVG(b.s_score)) from

student a

left join score b on a.s_id = b.s_id

where a.s_id in(

select s_id from score where s_score<60 GROUP BY s_id having count(1)>=2)

GROUP BY a.s_id,a.s_name

select a.*,b.c_id,b.s_score from

student a,score b

where a.s_id = b.s_id and b.c_id='01' and b.s_score<60 ORDER BY b.s_score DESC;

select a.s_id,(select s_score from score where s_id=a.s_id and c_id='01') as 语文,

(select s_score from score where s_id=a.s_id and c_id='02') as 数学,

(select s_score from score where s_id=a.s_id and c_id='03') as 英语,

round(avg(s_score),2) as 平均分 from score a GROUP BY a.s_id ORDER BY 平均分 DESC;

select a.c_id,b.c_name,MAX(s_score),MIN(s_score),ROUND(AVG(s_score),2),

ROUND(100*(SUM(case when a.s_score>=60 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 及格率,

ROUND(100*(SUM(case when a.s_score>=70 and a.s_score<=80 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 中等率,

ROUND(100*(SUM(case when a.s_score>=80 and a.s_score<=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 优良率,

ROUND(100*(SUM(case when a.s_score>=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 优秀率

from score a left join course b on a.c_id = b.c_id GROUP BY a.c_id,b.c_name

select a.s_id,a.c_id,

@i:=@i +1 as i保留排名,

@k:=(case when @score=a.s_score then @k else @i end) as rank不保留排名,

@score:=a.s_score as score

from (

select s_id,c_id,s_score from score WHERE c_id='01' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC

)a,(select @k:=0,@i:=0,@score:=0)s

union

select a.s_id,a.c_id,

@i:=@i +1 as i,

@k:=(case when @score=a.s_score then @k else @i end) as rank,

@score:=a.s_score as score

from (

select s_id,c_id,s_score from score WHERE c_id='02' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC

)a,(select @k:=0,@i:=0,@score:=0)s

union

select a.s_id,a.c_id,

@i:=@i +1 as i,

@k:=(case when @score=a.s_score then @k else @i end) as rank,

@score:=a.s_score as score

from (

select s_id,c_id,s_score from score WHERE c_id='03' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC

)a,(select @k:=0,@i:=0,@score:=0)s

select a.s_id,

@i:=@i+1 as i,

@k:=(case when @score=a.sum_score then @k else @i end) as rank,

@score:=a.sum_score as score

from (select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC)a,

(select @k:=0,@i:=0,@score:=0)s

select a.t_id,c.t_name,a.c_id,ROUND(avg(s_score),2) as avg_score from course a

left join score b on a.c_id=b.c_id

left join teacher c on a.t_id=c.t_id

GROUP BY a.c_id,a.t_id,c.t_name ORDER BY avg_score DESC;

select d.*,c.排名,c.s_score,c.c_id from (

select a.s_id,a.s_score,a.c_id,@i:=@i+1 as 排名 from score a,(select @i:=0)s where a.c_id='01'

)c

left join student d on c.s_id=d.s_id

where 排名 BETWEEN 2 AND 3

UNION

select d.*,c.排名,c.s_score,c.c_id from (

select a.s_id,a.s_score,a.c_id,@j:=@j+1 as 排名 from score a,(select @j:=0)s where a.c_id='02'

)c

left join student d on c.s_id=d.s_id

where 排名 BETWEEN 2 AND 3

UNION

select d.*,c.排名,c.s_score,c.c_id from (

select a.s_id,a.s_score,a.c_id,@k:=@k+1 as 排名 from score a,(select @k:=0)s where a.c_id='03'

)c

left join student d on c.s_id=d.s_id

where 排名 BETWEEN 2 AND 3;

select distinct f.c_name,a.c_id,b.`85-100`,b.百分比,c.`70-85`,c.百分比,d.`60-70`,d.百分比,e.`0-60`,e.百分比 from score a

left join (select c_id,SUM(case when s_score >85 and s_score <=100 then 1 else 0 end) as `85-100`,

ROUND(100*(SUM(case when s_score >85 and s_score <=100 then 1 else 0 end)/count(*)),2) as 百分比

from score GROUP BY c_id)b on a.c_id=b.c_id

left join (select c_id,SUM(case when s_score >70 and s_score <=85 then 1 else 0 end) as `70-85`,

ROUND(100*(SUM(case when s_score >70 and s_score <=85 then 1 else 0 end)/count(*)),2) as 百分比

from score GROUP BY c_id)c on a.c_id=c.c_id

left join (select c_id,SUM(case when s_score >60 and s_score <=70 then 1 else 0 end) as `60-70`,

ROUND(100*(SUM(case when s_score >60 and s_score <=70 then 1 else 0 end)/count(*)),2) as 百分比

from score GROUP BY c_id)d on a.c_id=d.c_id

left join (select c_id,SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end) as `0-60`,

ROUND(100*(SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end)/count(*)),2) as 百分比

from score GROUP BY c_id)e on a.c_id=e.c_id

left join course f on a.c_id = f.c_id

select a.s_id,

@i:=@i+1 as '不保留空缺排名',

@k:=(case when @avg_score=a.avg_s then @k else @i end) as '保留空缺排名',

@avg_score:=avg_s as '平均分'

from (select s_id,ROUND(AVG(s_score),2) as avg_s from score GROUP BY s_id)a,(select @avg_score:=0,@i:=0,@k:=0)b;

-- 1.选出b表比a表成绩大的所有组

-- 2.选出比当前id成绩大的 小于三个的

select a.s_id,a.c_id,a.s_score from score a

left join score b on a.c_id = b.c_id and a.s_score<b.s_score

group by a.s_id,a.c_id,a.s_score HAVING COUNT(b.s_id)<3

ORDER BY a.c_id,a.s_score DESC

select c_id,count(s_id) from score a GROUP BY c_id

select s_id,s_name from student where s_id in(

select s_id from score GROUP BY s_id HAVING COUNT(c_id)=2);

select s_sex,COUNT(s_sex) as 人数 from student GROUP BY s_sex

select * from student where s_name like '%风%';

select a.s_name,a.s_sex,count(*) from student a JOIN

student b on a.s_id !=b.s_id and a.s_name = b.s_name and a.s_sex = b.s_sex

GROUP BY a.s_name,a.s_sex

select s_name from student where s_birth like '1990%'

select c_id,ROUND(AVG(s_score),2) as avg_score from score GROUP BY c_id ORDER BY avg_score DESC,c_id ASC

select a.s_id,b.s_name,ROUND(avg(a.s_score),2) as avg_score from score a

left join student b on a.s_id=b.s_id GROUP BY s_id HAVING avg_score>=85

select a.s_name,b.s_score from score b LEFT JOIN student a on a.s_id=b.s_id where b.c_id=(

select c_id from course where c_name ='数学') and b.s_score<60

select a.s_id,a.s_name,

SUM(case c.c_name when '语文' then b.s_score else 0 end) as '语文',

SUM(case c.c_name when '数学' then b.s_score else 0 end) as '数学',

SUM(case c.c_name when '英语' then b.s_score else 0 end) as '英语',

SUM(b.s_score) as '总分'

from student a left join score b on a.s_id = b.s_id

left join course c on b.c_id = c.c_id

GROUP BY a.s_id,a.s_name

-- 36、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；

select a.s_name,b.c_name,c.s_score from course b left join score c on b.c_id = c.c_id

left join student a on a.s_id=c.s_id where c.s_score>=70

select a.s_id,a.c_id,b.c_name,a.s_score from score a left join course b on a.c_id = b.c_id

where a.s_score<60

select a.s_id,b.s_name from score a LEFT JOIN student b on a.s_id = b.s_id

where a.c_id = '01' and a.s_score>80

select count(*) from score GROUP BY c_id;

-- 查询老师id

select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='张三'

-- 查询最高分（可能有相同分数）

select MAX(s_score) from score where c_id='02'

-- 查询信息

select a.*,b.s_score,b.c_id,c.c_name from student a

LEFT JOIN score b on a.s_id = b.s_id

LEFT JOIN course c on b.c_id=c.c_id

where b.c_id =(select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='张三')

and b.s_score in (select MAX(s_score) from score where c_id='02')

select DISTINCT b.s_id,b.c_id,b.s_score from score a,score b where a.c_id != b.c_id and a.s_score = b.s_score

-- 牛逼的写法

select a.s_id,a.c_id,a.s_score from score a

where (select COUNT(1) from score b where b.c_id=a.c_id and b.s_score>=a.s_score)<=2 ORDER BY a.c_id

select c_id,count(*) as total from score GROUP BY c_id HAVING total>5 ORDER BY total,c_id ASC

select s_id,count(*) as sel from score GROUP BY s_id HAVING sel>=2

select * from student where s_id in(

select s_id from score GROUP BY s_id HAVING count(*)=(select count(*) from course))

-- 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

select s_birth,(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_birth,'%Y') -

(case when DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(s_birth,'%m%d') then 0 else 1 end)) as age

from student;

select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(s_birth)

select * from student where YEARWEEK(s_birth)=YEARWEEK(DATE_FORMAT(NOW(),'%Y%m%d'))

select WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))

select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =WEEK(s_birth)

select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d')) =MONTH(s_birth)

select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =MONTH(s_birth)