mysql练习题
1、表结构
–1.学生表
student(s_id,s_name,s_birth,s_sex) –学生编号,学生姓名, 出生年月,学生性别
–2.课程表
course(c_id,c_name,t_id) –课程编号, 课程名称, 教师编号
–3.教师表
teacher(t_id,t_name) –教师编号,教师姓名
–4.成绩表
score(s_id,c_id,s_score) –学生编号,课程编号,分数
2、测试数据
--建表
--学生表
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`)
);
--课程表
CREATE TABLE `Course`(
`c_id` VARCHAR(20),
`c_name` VARCHAR(20) NOT NULL DEFAULT '',
`t_id` VARCHAR(20) NOT NULL,
PRIMARY KEY(`c_id`)
);
--教师表
CREATE TABLE `Teacher`(
`t_id` VARCHAR(20),
`t_name` VARCHAR(20) NOT NULL DEFAULT '',
PRIMARY KEY(`t_id`)
);
--成绩表
CREATE TABLE `Score`(
`s_id` VARCHAR(20),
`c_id` VARCHAR(20),
`s_score` INT(3),
PRIMARY KEY(`s_id`,`c_id`)
);
--插入学生表测试数据
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');
--课程表测试数据
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
--教师表测试数据
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');
--成绩表测试数据
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);
3、测试题
-- 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 s.*, t1.s_score, t2.s_score from student s
inner join score t1 on s.s_id = t1.s_id and t1.c_id = '01'
left join score t2 on s.s_id = t2.s_id and t2.c_id = '02' or t2.c_id = NULL
where t1.s_score > t2.s_score;
select s.*, t1.s_score, t2.s_score
from
(select s_id, s_score from score where c_id = '01') t1
inner join
(select s_id, s_score from score where c_id = '02') t2 on t1.s_id = t2.s_id
left join student s on s.s_id = t1.s_id
where t1.s_score > t2.s_score;
select s.*,t1.s_score,t2.s_score from student s
LEFT join score t1 on s.s_id = t1.s_id and t1.c_id = '01'
LEFT join score t2 on t1.s_id = t2.s_id and t2.c_id = '02'
where t1.s_score > t2.s_score;
-- 2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数
select s.*, t1.s_score, t2.s_score from student s
left join score t1 on s.s_id = t1.s_id and t1.c_id = '01' or t1.c_id = NULL
join score t2 on s.s_id = t2.s_id and t2.c_id = '02'
where t1.s_score < t2.s_score;
select s.*, t1.s_score, t2.s_score
from
(select s_id, s_score from score where c_id = '01') t1
inner join
(select s_id, s_score from score where c_id = '02') t2 on t1.s_id = t2.s_id
left join student s on s.s_id = t1.s_id
where t1.s_score < t2.s_score;
select s.*,t1.s_score,t2.s_score from student s
LEFT join score t1 on s.s_id = t1.s_id and t1.c_id = '01'
LEFT join score t2 on t1.s_id = t2.s_id and t2.c_id = '02'
where t1.s_score < t2.s_score;
-- 3、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
select s.s_id, s.s_name, ROUND(AVG(t.s_score), 2) as avg_score
from student s
join score t on s.s_id = t.s_id
group by t.s_id, s.s_name
having avg_score >= 60;
select s.s_id,s.s_name,ROUND(AVG(t.s_score),2) as avg_score from student s,score t
where s.s_id = t.s_id
group by t.s_id
having avg_score>=60;
-- 4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩
#(包括有成绩的和无成绩的)
select s.s_id,s.s_name,ROUND(AVG(t.s_score),2) as avg_score
from student s
left join score t on s.s_id = t.s_id
group by s.s_id,s.s_name
having avg_score < 60
union
select s.s_id,s.s_name,ROUND(0,2) as avg_score
from student s
where s.s_id not in (select s_id from score group by s_id);
-- 5、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
select s.s_id,s.s_name,count(t.c_id) as sum_course,ifnull(sum(t.s_score),0) as sum_score
from student s
left join score t on s.s_id=t.s_id
group by s.s_id,s.s_name;
-- 6、查询"李"姓老师的数量
select count(t_id) as t_count from teacher where t_name like '李%';
-- 7、查询学过"张三"老师授课的同学的信息
select s.* from student s
inner join score t on t.s_id = s.s_id
where t.c_id in (select c_id from course where t_id=(select t_id from teacher where t_name ='张三'));
-- 8、查询没学过"张三"老师授课的同学的信息
select * from student
where s_id not in(
select s.s_id from student s
inner join score t on s.s_id=t.s_id where t.c_id in(
select c_id from course where t_id =(
select t_id from teacher where t_name = '张三')));
-- 9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息
select s.* from
student s,score t1,score t2
where s.s_id = t1.s_id and s.s_id = t2.s_id and t1.c_id='01' and t2.c_id='02';
select s.*
from
(select s_id, s_score from score where c_id = '01') t1
inner join
(select s_id, s_score from score where c_id = '02') t2 on t1.s_id = t2.s_id
left join student s on s.s_id = t1.s_id;
-- 10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息
select * from student where s_id in (
select s_id from score where c_id='01')
and s_id not in(
select s_id from score where c_id='02');
select s.* from student s
inner join score t1 on t1.s_id = s.s_id and t1.c_id = '01'
left join score t2 on t2.s_id = s.s_id and t2.c_id = '02'
where t2.s_id is null and t2.c_id is null;
-- 11、查询没有学全所有课程的同学的信息
select * from student where s_id in(
select s_id from score where s_id not in(select a.s_id from score a
inner join score b on a.s_id = b.s_id and b.c_id='02'
inner join score c on a.s_id = c.s_id and c.c_id='03'
where a.c_id='01') group by s_id);
#查询所有课程没有选的或者一课都没选的同学的信息
select s.* from student s
left join score t1 on t1.s_id = s.s_id and t1.c_id = '01'
left join score t2 on t2.s_id = s.s_id and t2.c_id = '02'
left join score t3 on t3.s_id = s.s_id and t3.c_id = '03'
where t1.s_id is null or t2.s_id is null or t3.s_id is null;
-- 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
select * from student
where s_id in (
select s_id from score where c_id in (
select c_id from score where s_id = '01')
group by s_id);
-- 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
select * from student where s_id in(
select 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'));
-- 14、查询没学过"张三"老师讲授的任一门课程的学生姓名
select s_name from student where 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);
-- 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
select s.s_id,s.s_name,ROUND(AVG(t.s_score)) as avg_score from student s
left join score t on s.s_id = t.s_id
where s.s_id in(
select s_id from score where s_score<60
GROUP BY s_id having count(1)>=2)
GROUP BY s.s_id,s.s_name;
select s.s_id,s.s_name, ROUND(AVG(t.s_score),2) from student s,score t
where s.s_id = t.s_id
and s.s_id in (select s_id from score where s_score < 60
group by s_id
having count(1) >=2)
group by s.s_id, s.s_name;
-- 16、检索"01"课程分数小于60，按分数降序排列的学生信息
select s.*,t.c_id,t.s_score from
student s,score t
where s.s_id = t.s_id and t.c_id='01' and t.s_score<60
ORDER BY t.s_score DESC;
-- 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
#查询学生语文的成绩
select s_score from score where s_id='01' and c_id='01';
#查询学生数学的成绩
select s_score from score where s_id='01' and c_id='02';
#查询学生英语的成绩
select s_score from score where s_id='01' and c_id='03';
#查询全部的条件
select s.s_id,
(select s_score from score where s_id=s.s_id and c_id='01') as 语文,
(select s_score from score where s_id=s.s_id and c_id='02') as 数学,
(select s_score from score where s_id=s.s_id and c_id='03') as 英语,
ROUND(AVG(s.s_score),2) as 平均分 from score s
GROUP BY s.s_id
ORDER BY 平均分 DESC;
-- 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
select s.c_id,t.c_name,MAX(s_score) as max_score ,MIN(s_score) as min_score,ROUND(AVG(s_score),2) as avg_score,
ROUND(100*(SUM(case when s.s_score>=60 then 1 else 0 end)/SUM(case when s.s_score then 1 else 0 end)),2) as 及格率,
ROUND(100*(SUM(case when s.s_score>=70 and s.s_score<=80 then 1 else 0 end)/SUM(case when s.s_score then 1 else 0 end)),2) as 中等率,
ROUND(100*(SUM(case when s.s_score>=80 and s.s_score<=90 then 1 else 0 end)/SUM(case when s.s_score then 1 else 0 end)),2) as 优良率,
ROUND(100*(SUM(case when s.s_score>=90 then 1 else 0 end)/SUM(case when s.s_score then 1 else 0 end)),2) as 优秀率
from score s
left join course t on s.c_id = t.c_id
GROUP BY s.c_id,t.c_name;
-- 19、按各科成绩进行排序，并显示排名
#查询每科的排名 以01为例
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;
#使用临时变量@表示 @i ,@j 排名 以01为例 注意查询单科表示排名的临时变量名不能相同。
select a.s_id,a.c_id,
@i:=@i +1 as rank1,#不保留空缺排名
@j:=(case when @score=a.s_score then @j else @i end) as rank2,#保留空缺排名
@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 @j:=0,@i:=0,@score:=0)s;
#查询所有信息
select a.s_id,a.c_id,
@i:=@i +1 as rank1,
@j:=(case when @score=a.s_score then @j else @i end) as rank2,
@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 @j:=0,@i:=0,@score:=0)s
union
select a.s_id,a.c_id,
@m:=@m +1 as rank1,
@n:=(case when @score=a.s_score then @n else @m end) as rank2,
@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 @n:=0,@m:=0,@score:=0)s
union
select a.s_id,a.c_id,
@p:=@p +1 as rank1,
@q:=(case when @score=a.s_score then @q else @p end) as rank2,
@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 @q:=0,@p:=0,@score:=0)s;
-- 20、查询学生的总成绩并进行排名
#查询出总成绩并排序
select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC;
#查询所有信息
select a.s_id,
@i:=@i+1 as rank1,
@j:=(case when @score=a.sum_score then @j else @i end) as rank2,
@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 @j:=0,@i:=0,@score:=0)b;
-- 21、查询不同老师所教不同课程平均分从高到低显示
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;
-- 22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩
#查询排名 以01为例
select a.s_id,a.s_score,a.c_id,
@i:=@i+1 as rank1,#不保留空缺排名
@j:=(case when @score=a.s_score then @j else @i end) as rank2,#保留空缺排名
@score:=a.s_score as score
from score a,(select @i:=0,@j:=0,@score:=0)s
where a.c_id='01'
order by a.s_score DESC;
#查询成绩第2名到第3名的学生信息及该课程成绩
select d.*,c.rank2,c.s_score,c.c_id
from (select a.s_id,a.s_score,a.c_id,
@i:=@i+1 as rank1,#不保留空缺排名
@j:=(case when @score=a.s_score then @j else @i end) as rank2,#保留空缺排名
@score:=a.s_score as score
from score a,(select @i:=0,@j:=0,@score:=0)s
where a.c_id='01'
order by a.s_score DESC)c
left join student d on c.s_id=d.s_id
where c.rank2 between 2 and 3;
#查询所有信息
select d.*,c.rank2,c.s_score,c.c_id
from (select a.s_id,a.s_score,a.c_id,
@i:=@i+1 as rank1,
@j:=(case when @score=a.s_score then @j else @i end) as rank2,
@score:=a.s_score as score
from score a,(select @i:=0,@j:=0,@score:=0)s
where a.c_id='01'
order by a.s_score DESC)c
left join student d on c.s_id=d.s_id
where c.rank2 between 2 and 3
UNION
select d.*,c.rank2,c.s_score,c.c_id
from (select a.s_id,a.s_score,a.c_id,
@m:=@m+1 as rank1,
@n:=(case when @score=a.s_score then @n else @m end) as rank2,
@score:=a.s_score as score
from score a,(select @m:=0,@n:=0,@score:=0)s
where a.c_id='02'
order by a.s_score DESC)c
left join student d on c.s_id=d.s_id
where c.rank2 between 2 and 3
UNION
select d.*,c.rank2,c.s_score,c.c_id
from (select a.s_id,a.s_score,a.c_id,
@p:=@p+1 as rank1,
@q:=(case when @score=a.s_score then @q else @p end) as rank2,
@score:=a.s_score as score
from score a,(select @p:=0,@q:=0,@score:=0)s
where a.c_id='03'
order by a.s_score DESC)c
left join student d on c.s_id=d.s_id
where c.rank2 between 2 and 3;
-- 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],[0-60]及所占百分比
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;
-- 24、查询学生平均成绩及其名次
select a.s_id,
@i:=@i+1 as rank1,#不保留空缺排名
@k:=(case when @avg_score=a.avg then @k else @i end) as rank2,#'保留空缺排名'
@avg_score:=a.avg as avg_score
from (select s_id,ROUND(AVG(s_score),2) as avg from score GROUP BY s_id order by avg DESC )a,(select @avg_score:=0,@i:=0,@k:=0)b;#@临时变量赋初值
-- 25、查询各科成绩前三名的记录
# 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;
-- 26、查询每门课程被选修的学生数
select c_id,count(s_id) from score a GROUP BY c_id;
-- 27、查询出只有两门课程的全部学生的学号和姓名
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);
-- 28、查询男生、女生人数
select s_sex,COUNT(s_sex) as 人数 from student GROUP BY s_sex;
-- 29、查询名字中含有"风"字的学生信息
select * from student where s_name like '%风%';
-- 30、查询同名同性学生名单，并统计同名人数
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;
-- 31、查询1990年出生的学生名单
select s_name from student where s_birth like '1990%';
-- 32、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
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;
-- 33、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
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;
-- 34、查询课程名称为"数学"，且分数低于60的学生姓名和分数
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;
-- 35、查询所有学生的课程及分数情况
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;
-- 37、查询不及格的课程
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 ;
-- 38、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
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;
-- 39、求每门课程的学生人数
select count(*) from score
group by c_id;
-- 40、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
#查询老师id
select c_id from course c,teacher t
where c.t_id=t.t_id and t.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 t where c.t_id=t.t_id and t.t_name='张三')
and b.s_score in (select MAX(s_score) from score where c_id='02');
-- 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
select distinct t.s_id,t.c_id,t.s_score from score s,score t
where s.c_id != t.c_id and s.s_score = t.s_score;
-- 42、查询每门功成绩最好的前两名
# 牛逼的写法
select s.s_id,s.c_id,s.s_score from score s
where (select COUNT(1) from score t where t.c_id=s.c_id and t.s_score>=s.s_score)<=2
order by s.c_id;
-- 43、统计每门课程的学生选修人数（超过5人的课程才统计）。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
select c_id,count(*) as total from score
group by c_id
having total>5
order by total,c_id asc;
-- 44、检索至少选修两门课程的学生学号
select s_id,count(*) as sel from score
group by s_id
having sel>=2;
-- 45、查询选修了全部课程的学生信息
select * from student
where s_id in(select s_id from score group by s_id having count(*)=(select count(*) from course));
-- 46、查询各学生的年龄
# 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;
-- 47、查询本周过生日的学生
#YEARWEEK 是获取年份和周数的一个函数，函数形式为 YEARWEEK(date,[mode])
select YEARWEEK('2020-02-02');# = 202005
select YEARWEEK(NOW());
select YEARWEEK(CURDATE());
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'));
#WEEKOFYEAR函数是计算出当前日期所在周数，和YEARWEEK('日期',1)的周数一致，但YEARWEEK('日期',1)在小于10的时候，不带0
select WEEKOFYEAR('2020-02-02');# = 5
select WEEKOFYEAR(NOW());
select WEEK(NOW());
select NOW();
select CURDATE();
select * from student where WEEKOFYEAR(s_birth)=WEEKOFYEAR(CURDATE());
-- 48、查询下周过生日的学生
select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =WEEK(s_birth);
select * from student where WEEKOFYEAR(CURDATE())+1 = WEEKOFYEAR(s_birth);
-- 49、查询本月过生日的学生
select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d')) =MONTH(s_birth);
select * from student where DATE_FORMAT(s_birth,'%m') - DATE_FORMAT(NOW(),'%m') = 0;
-- 50、查询下月过生日的学生
select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =MONTH(s_birth);
select * from student where DATE_FORMAT(s_birth,'%m') - DATE_FORMAT(NOW(),'%m') = 1;
select * from student where MONTH(DATE_ADD(NOW(),INTERVAL 1 month)) = MONTH(s_birth);