sql语句练习50题(Mysql版)
表名和字段
–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
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);
练习题和sql语句
-- 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 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
–也可以这样写
select a.*,b.s_score as 01_score,c.s_score as 02_score 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’
and b.s_score>c.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 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
– 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 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 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 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 avg_score <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);
– 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 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;
– 6、查询"李"姓老师的数量
select count(t_id) 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 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’));
– 8、查询没学过"张三"老师授课的同学的信息
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 a.c_id from course a join teacher b on a.t_id = b.t_id 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 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’;
– 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 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’)
– 11、查询没有学全所有课程的同学的信息
–@wendiepei的写法
select s. from student s
left join Score s1 on s1.s_id=s.s_id
group by s.s_id having count(s1.c_id)<(select count() from course)
–@k1051785839的写法
select
from student
where s_id not in(
select s_id from score t1
group by s_id having count() =(select count(distinct c_id) from course))
– 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 distinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.s_id=‘01’)
);
– 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
–@ouyang_1993的写法
SELECT
Student.
FROM
Student
WHERE
s_id IN (SELECT s_id FROM Score GROUP BY s_id HAVING COUNT(s_id) = (
#下面的语句是找到’01’同学学习的课程数
SELECT COUNT(c_id) FROM Score WHERE s_id = ‘01’
)
)
AND s_id NOT IN (
#下面的语句是找到学过‘01’同学没学过的课程，有哪些同学。并排除他们
SELECT s_id FROM Score
WHERE c_id IN(
#下面的语句是找到‘01’同学没学过的课程
SELECT DISTINCT c_id FROM Score
WHERE c_id NOT IN (
#下面的语句是找出‘01’同学学习的课程
SELECT c_id FROM Score WHERE s_id = ‘01’
)
) GROUP BY s_id
) #下面的条件是排除01同学
AND s_id NOT IN (‘01’)
–@k1051785839的写法
SELECT
t3.
FROM
(
SELECT
s_id,
group_concat(c_id ORDER BY c_id) group1
FROM
score
WHERE
s_id <> ‘01’
GROUP BY
s_id
) t1
INNER JOIN (
SELECT
group_concat(c_id ORDER BY c_id) group2
FROM
score
WHERE
s_id = ‘01’
GROUP BY
s_id
) t2 ON t1.group1 = t2.group2
INNER JOIN student t3 ON t1.s_id = t3.s_id
– 14、查询没学过"张三"老师讲授的任一门课程的学生姓名
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’)));
– 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 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
– 16、检索"01"课程分数小于60，按分数降序排列的学生信息
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;
– 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
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;
–@喝完这杯还有一箱的写法
SELECT a.s_id,MAX(CASE a.c_id WHEN ‘01’ THEN a.s_score END ) 语文,
MAX(CASE a.c_id WHEN ‘02’ THEN a.s_score END ) 数学,
MAX(CASE a.c_id WHEN ‘03’ THEN a.s_score END ) 英语,
avg(a.s_score),b.s_name FROM Score a JOIN Student b ON a.s_id=b.s_id GROUP BY a.s_id ORDER BY 5 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 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
– 19、按各科成绩进行排序，并显示排名
– mysql没有rank函数
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 GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s
–@k1051785839的写法
(select from (select
t1.c_id,
t1.s_score,
(select count(distinct t2.s_score) from score t2 where t2.s_score>=t1.s_score and t2.c_id=‘01’) rank
FROM score t1 where t1.c_id=‘01’
order by t1.s_score desc) t1)
union
(select from (select
t1.c_id,
t1.s_score,
(select count(distinct t2.s_score) from score t2 where t2.s_score>=t1.s_score and t2.c_id=‘02’) rank
FROM score t1 where t1.c_id=‘02’
order by t1.s_score desc) t2)
union
(select * from (select
t1.c_id,
t1.s_score,
(select count(distinct t2.s_score) from score t2 where t2.s_score>=t1.s_score and t2.c_id=‘03’) rank
FROM score t1 where t1.c_id=‘03’
order by t1.s_score desc) t3)
– 20、查询学生的总成绩并进行排名
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
– 21、查询不同老师所教不同课程平均分从高到低显示
<span class="token keyword">select</span> a<span class="token punctuation">.</span>t_id<span class="token punctuation">,</span>c<span class="token punctuation">.</span>t_name<span class="token punctuation">,</span>a<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span><span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token function">avg</span><span class="token punctuation">(</span>s_score<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> avg_score <span class="token keyword">from</span> course a <span class="token keyword">left</span> <span class="token keyword">join</span> score b <span class="token keyword">on</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span>b<span class="token punctuation">.</span>c_id <span class="token keyword">left</span> <span class="token keyword">join</span> teacher c <span class="token keyword">on</span> a<span class="token punctuation">.</span>t_id<span class="token operator">=</span>c<span class="token punctuation">.</span>t_id <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> a<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span>a<span class="token punctuation">.</span>t_id<span class="token punctuation">,</span>c<span class="token punctuation">.</span>t_name <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> avg_score <span class="token keyword">DESC</span><span class="token punctuation">;</span>
– 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
<span class="token keyword">select</span> d<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">,</span>c<span class="token punctuation">.</span>排名<span class="token punctuation">,</span>c<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>c<span class="token punctuation">.</span>c_id <span class="token keyword">from</span> <span class="token punctuation">(</span> <span class="token keyword">select</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span>a<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>a<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span><span class="token variable">@i</span>:<span class="token operator">=</span><span class="token variable">@i</span><span class="token operator">+</span><span class="token number">1</span> <span class="token keyword">as</span> 排名 <span class="token keyword">from</span> score a<span class="token punctuation">,</span><span class="token punctuation">(</span><span class="token keyword">select</span> <span class="token variable">@i</span>:<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span>s <span class="token keyword">where</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span><span class="token string">'01'</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">.</span>s_score <span class="token keyword">DESC</span> <span class="token punctuation">)</span>c <span class="token keyword">left</span> <span class="token keyword">join</span> student d <span class="token keyword">on</span> c<span class="token punctuation">.</span>s_id<span class="token operator">=</span>d<span class="token punctuation">.</span>s_id <span class="token keyword">where</span> 排名 <span class="token operator">BETWEEN</span> <span class="token number">2</span> <span class="token operator">AND</span> <span class="token number">3</span> <span class="token keyword">UNION</span> <span class="token keyword">select</span> d<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">,</span>c<span class="token punctuation">.</span>排名<span class="token punctuation">,</span>c<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>c<span class="token punctuation">.</span>c_id <span class="token keyword">from</span> <span class="token punctuation">(</span> <span class="token keyword">select</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span>a<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>a<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span><span class="token variable">@j</span>:<span class="token operator">=</span><span class="token variable">@j</span><span class="token operator">+</span><span class="token number">1</span> <span class="token keyword">as</span> 排名 <span class="token keyword">from</span> score a<span class="token punctuation">,</span><span class="token punctuation">(</span><span class="token keyword">select</span> <span class="token variable">@j</span>:<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span>s <span class="token keyword">where</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span><span class="token string">'02'</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">.</span>s_score <span class="token keyword">DESC</span> <span class="token punctuation">)</span>c <span class="token keyword">left</span> <span class="token keyword">join</span> student d <span class="token keyword">on</span> c<span class="token punctuation">.</span>s_id<span class="token operator">=</span>d<span class="token punctuation">.</span>s_id <span class="token keyword">where</span> 排名 <span class="token operator">BETWEEN</span> <span class="token number">2</span> <span class="token operator">AND</span> <span class="token number">3</span> <span class="token keyword">UNION</span> <span class="token keyword">select</span> d<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">,</span>c<span class="token punctuation">.</span>排名<span class="token punctuation">,</span>c<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>c<span class="token punctuation">.</span>c_id <span class="token keyword">from</span> <span class="token punctuation">(</span> <span class="token keyword">select</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span>a<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>a<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span><span class="token variable">@k</span>:<span class="token operator">=</span><span class="token variable">@k</span><span class="token operator">+</span><span class="token number">1</span> <span class="token keyword">as</span> 排名 <span class="token keyword">from</span> score a<span class="token punctuation">,</span><span class="token punctuation">(</span><span class="token keyword">select</span> <span class="token variable">@k</span>:<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span>s <span class="token keyword">where</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span><span class="token string">'03'</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> a<span class="token punctuation">.</span>s_score <span class="token keyword">DESC</span> <span class="token punctuation">)</span>c <span class="token keyword">left</span> <span class="token keyword">join</span> student d <span class="token keyword">on</span> c<span class="token punctuation">.</span>s_id<span class="token operator">=</span>d<span class="token punctuation">.</span>s_id <span class="token keyword">where</span> 排名 <span class="token operator">BETWEEN</span> <span class="token number">2</span> <span class="token operator">AND</span> <span class="token number">3</span><span class="token punctuation">;</span>
– 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
<span class="token keyword">select</span> <span class="token keyword">distinct</span> f<span class="token punctuation">.</span>c_name<span class="token punctuation">,</span>a<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span>b<span class="token punctuation">.</span><span class="token punctuation">`</span><span class="token number">85</span><span class="token operator">-</span><span class="token number">100</span><span class="token punctuation">`</span><span class="token punctuation">,</span>b<span class="token punctuation">.</span>百分比<span class="token punctuation">,</span>c<span class="token punctuation">.</span><span class="token punctuation">`</span><span class="token number">70</span><span class="token operator">-</span><span class="token number">85</span><span class="token punctuation">`</span><span class="token punctuation">,</span>c<span class="token punctuation">.</span>百分比<span class="token punctuation">,</span>d<span class="token punctuation">.</span><span class="token punctuation">`</span><span class="token number">60</span><span class="token operator">-</span><span class="token number">70</span><span class="token punctuation">`</span><span class="token punctuation">,</span>d<span class="token punctuation">.</span>百分比<span class="token punctuation">,</span>e<span class="token punctuation">.</span><span class="token punctuation">`</span><span class="token number">0</span><span class="token operator">-</span><span class="token number">60</span><span class="token punctuation">`</span><span class="token punctuation">,</span>e<span class="token punctuation">.</span>百分比 <span class="token keyword">from</span> score a <span class="token keyword">left</span> <span class="token keyword">join</span> <span class="token punctuation">(</span><span class="token keyword">select</span> c_id<span class="token punctuation">,</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">></span><span class="token number">85</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">100</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token punctuation">`</span><span class="token number">85</span><span class="token operator">-</span><span class="token number">100</span><span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token operator">*</span><span class="token punctuation">(</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">></span><span class="token number">85</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">100</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span><span class="token operator">/</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> 百分比 <span class="token keyword">from</span> score <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c_id<span class="token punctuation">)</span>b <span class="token keyword">on</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span>b<span class="token punctuation">.</span>c_id <span class="token keyword">left</span> <span class="token keyword">join</span> <span class="token punctuation">(</span><span class="token keyword">select</span> c_id<span class="token punctuation">,</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">></span><span class="token number">70</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">85</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token punctuation">`</span><span class="token number">70</span><span class="token operator">-</span><span class="token number">85</span><span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token operator">*</span><span class="token punctuation">(</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">></span><span class="token number">70</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">85</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span><span class="token operator">/</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> 百分比 <span class="token keyword">from</span> score <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c_id<span class="token punctuation">)</span>c <span class="token keyword">on</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span>c<span class="token punctuation">.</span>c_id <span class="token keyword">left</span> <span class="token keyword">join</span> <span class="token punctuation">(</span><span class="token keyword">select</span> c_id<span class="token punctuation">,</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">></span><span class="token number">60</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">70</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token punctuation">`</span><span class="token number">60</span><span class="token operator">-</span><span class="token number">70</span><span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token operator">*</span><span class="token punctuation">(</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">></span><span class="token number">60</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">70</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span><span class="token operator">/</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> 百分比 <span class="token keyword">from</span> score <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c_id<span class="token punctuation">)</span>d <span class="token keyword">on</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span>d<span class="token punctuation">.</span>c_id <span class="token keyword">left</span> <span class="token keyword">join</span> <span class="token punctuation">(</span><span class="token keyword">select</span> c_id<span class="token punctuation">,</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">>=</span><span class="token number">0</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">60</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token punctuation">`</span><span class="token number">0</span><span class="token operator">-</span><span class="token number">60</span><span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token operator">*</span><span class="token punctuation">(</span><span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> s_score <span class="token operator">>=</span><span class="token number">0</span> <span class="token operator">and</span> s_score <span class="token operator"><=</span><span class="token number">60</span> <span class="token keyword">then</span> <span class="token number">1</span> <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span><span class="token operator">/</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> 百分比 <span class="token keyword">from</span> score <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c_id<span class="token punctuation">)</span>e <span class="token keyword">on</span> a<span class="token punctuation">.</span>c_id<span class="token operator">=</span>e<span class="token punctuation">.</span>c_id <span class="token keyword">left</span> <span class="token keyword">join</span> course f <span class="token keyword">on</span> a<span class="token punctuation">.</span>c_id <span class="token operator">=</span> f<span class="token punctuation">.</span>c_id
– 24、查询学生平均成绩及其名次
<span class="token keyword">select</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span> <span class="token variable">@i</span>:<span class="token operator">=</span><span class="token variable">@i</span><span class="token operator">+</span><span class="token number">1</span> <span class="token keyword">as</span> <span class="token string">'不保留空缺排名'</span><span class="token punctuation">,</span> <span class="token variable">@k</span>:<span class="token operator">=</span><span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> <span class="token variable">@avg_score</span><span class="token operator">=</span>a<span class="token punctuation">.</span>avg_s <span class="token keyword">then</span> <span class="token variable">@k</span> <span class="token keyword">else</span> <span class="token variable">@i</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token string">'保留空缺排名'</span><span class="token punctuation">,</span> <span class="token variable">@avg_score</span>:<span class="token operator">=</span>avg_s <span class="token keyword">as</span> <span class="token string">'平均分'</span> <span class="token keyword">from</span> <span class="token punctuation">(</span><span class="token keyword">select</span> s_id<span class="token punctuation">,</span><span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token function">AVG</span><span class="token punctuation">(</span>s_score<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> avg_s <span class="token keyword">from</span> score <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> s_id <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> avg_s <span class="token keyword">DESC</span><span class="token punctuation">)</span>a<span class="token punctuation">,</span><span class="token punctuation">(</span><span class="token keyword">select</span> <span class="token variable">@avg_score</span>:<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">,</span><span class="token variable">@i</span>:<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">,</span><span class="token variable">@k</span>:<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span>b<span class="token punctuation">;</span>
– 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
<span class="token keyword">select</span> c_id<span class="token punctuation">,</span><span class="token function">count</span><span class="token punctuation">(</span>s_id<span class="token punctuation">)</span> <span class="token keyword">from</span> score a <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> 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
<span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> student <span class="token keyword">where</span> s_name <span class="token operator">like</span> <span class="token string">'%风%'</span><span class="token punctuation">;</span>
– 30、查询同名同性学生名单，并统计同名人数
<span class="token keyword">select</span> a<span class="token punctuation">.</span>s_name<span class="token punctuation">,</span>a<span class="token punctuation">.</span>s_sex<span class="token punctuation">,</span><span class="token function">count</span><span class="token punctuation">(</span><span class="token operator">*</span><span class="token punctuation">)</span> <span class="token keyword">from</span> student a <span class="token keyword">JOIN</span> student b <span class="token keyword">on</span> a<span class="token punctuation">.</span>s_id <span class="token operator">!=</span>b<span class="token punctuation">.</span>s_id <span class="token operator">and</span> a<span class="token punctuation">.</span>s_name <span class="token operator">=</span> b<span class="token punctuation">.</span>s_name <span class="token operator">and</span> a<span class="token punctuation">.</span>s_sex <span class="token operator">=</span> b<span class="token punctuation">.</span>s_sex <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> a<span class="token punctuation">.</span>s_name<span class="token punctuation">,</span>a<span class="token punctuation">.</span>s_sex
– 31、查询1990年出生的学生名单
<span class="token keyword">select</span> s_name <span class="token keyword">from</span> student <span class="token keyword">where</span> s_birth <span class="token operator">like</span> <span class="token string">'1990%'</span>
– 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
<span class="token keyword">select</span> c_id<span class="token punctuation">,</span><span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token function">AVG</span><span class="token punctuation">(</span>s_score<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> avg_score <span class="token keyword">from</span> score <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> c_id <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> avg_score <span class="token keyword">DESC</span><span class="token punctuation">,</span>c_id <span class="token keyword">ASC</span>
– 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
<span class="token keyword">select</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span>b<span class="token punctuation">.</span>s_name<span class="token punctuation">,</span><span class="token function">ROUND</span><span class="token punctuation">(</span><span class="token function">avg</span><span class="token punctuation">(</span>a<span class="token punctuation">.</span>s_score<span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token keyword">as</span> avg_score <span class="token keyword">from</span> score a <span class="token keyword">left</span> <span class="token keyword">join</span> student b <span class="token keyword">on</span> a<span class="token punctuation">.</span>s_id<span class="token operator">=</span>b<span class="token punctuation">.</span>s_id <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> s_id <span class="token keyword">HAVING</span> avg_score<span class="token operator">>=</span><span class="token number">85</span>
– 34、查询课程名称为"数学"，且分数低于60的学生姓名和分数
<span class="token keyword">select</span> a<span class="token punctuation">.</span>s_name<span class="token punctuation">,</span>b<span class="token punctuation">.</span>s_score <span class="token keyword">from</span> score b <span class="token keyword">join</span> student a <span class="token keyword">on</span> a<span class="token punctuation">.</span>s_id<span class="token operator">=</span>b<span class="token punctuation">.</span>s_id <span class="token keyword">where</span> b<span class="token punctuation">.</span>c_id<span class="token operator">=</span><span class="token punctuation">(</span> <span class="token keyword">select</span> c_id <span class="token keyword">from</span> course <span class="token keyword">where</span> c_name <span class="token operator">=</span><span class="token string">'数学'</span><span class="token punctuation">)</span> <span class="token operator">and</span> b<span class="token punctuation">.</span>s_score<span class="token operator"><</span><span class="token number">60</span>
– 35、查询所有学生的课程及分数情况；
<span class="token keyword">select</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span>a<span class="token punctuation">.</span>s_name<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> c<span class="token punctuation">.</span>c_name <span class="token keyword">when</span> <span class="token string">'语文'</span> <span class="token keyword">then</span> b<span class="token punctuation">.</span>s_score <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token string">'语文'</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> c<span class="token punctuation">.</span>c_name <span class="token keyword">when</span> <span class="token string">'数学'</span> <span class="token keyword">then</span> b<span class="token punctuation">.</span>s_score <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token string">'数学'</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span><span class="token keyword">case</span> c<span class="token punctuation">.</span>c_name <span class="token keyword">when</span> <span class="token string">'英语'</span> <span class="token keyword">then</span> b<span class="token punctuation">.</span>s_score <span class="token keyword">else</span> <span class="token number">0</span> <span class="token keyword">end</span><span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token string">'英语'</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>b<span class="token punctuation">.</span>s_score<span class="token punctuation">)</span> <span class="token keyword">as</span> <span class="token string">'总分'</span> <span class="token keyword">from</span> student a <span class="token keyword">left</span> <span class="token keyword">join</span> score b <span class="token keyword">on</span> a<span class="token punctuation">.</span>s_id <span class="token operator">=</span> b<span class="token punctuation">.</span>s_id <span class="token keyword">left</span> <span class="token keyword">join</span> course c <span class="token keyword">on</span> b<span class="token punctuation">.</span>c_id <span class="token operator">=</span> c<span class="token punctuation">.</span>c_id <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> a<span class="token punctuation">.</span>s_id<span class="token punctuation">,</span>a<span class="token punctuation">.</span>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
<span class="token comment">-- 查询老师id </span> <span class="token keyword">select</span> c_id <span class="token keyword">from</span> course c<span class="token punctuation">,</span>teacher d <span class="token keyword">where</span> c<span class="token punctuation">.</span>t_id<span class="token operator">=</span>d<span class="token punctuation">.</span>t_id <span class="token operator">and</span> d<span class="token punctuation">.</span>t_name<span class="token operator">=</span><span class="token string">'张三'</span> <span class="token comment">-- 查询最高分（可能有相同分数）</span> <span class="token keyword">select</span> <span class="token function">MAX</span><span class="token punctuation">(</span>s_score<span class="token punctuation">)</span> <span class="token keyword">from</span> score <span class="token keyword">where</span> c_id<span class="token operator">=</span><span class="token string">'02'</span> <span class="token comment">-- 查询信息</span> <span class="token keyword">select</span> a<span class="token punctuation">.</span><span class="token operator">*</span><span class="token punctuation">,</span>b<span class="token punctuation">.</span>s_score<span class="token punctuation">,</span>b<span class="token punctuation">.</span>c_id<span class="token punctuation">,</span>c<span class="token punctuation">.</span>c_name <span class="token keyword">from</span> student a <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> score b <span class="token keyword">on</span> a<span class="token punctuation">.</span>s_id <span class="token operator">=</span> b<span class="token punctuation">.</span>s_id <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> course c <span class="token keyword">on</span> b<span class="token punctuation">.</span>c_id<span class="token operator">=</span>c<span class="token punctuation">.</span>c_id <span class="token keyword">where</span> b<span class="token punctuation">.</span>c_id <span class="token operator">=</span><span class="token punctuation">(</span><span class="token keyword">select</span> c_id <span class="token keyword">from</span> course c<span class="token punctuation">,</span>teacher d <span class="token keyword">where</span> c<span class="token punctuation">.</span>t_id<span class="token operator">=</span>d<span class="token punctuation">.</span>t_id <span class="token operator">and</span> d<span class="token punctuation">.</span>t_name<span class="token operator">=</span><span class="token string">'张三'</span><span class="token punctuation">)</span> <span class="token operator">and</span> b<span class="token punctuation">.</span>s_score <span class="token operator">in</span> <span class="token punctuation">(</span><span class="token keyword">select</span> <span class="token function">MAX</span><span class="token punctuation">(</span>s_score<span class="token punctuation">)</span> <span class="token keyword">from</span> score <span class="token keyword">where</span> c_id<span class="token operator">=</span><span class="token string">'02'</span><span class="token punctuation">)</span>
– 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 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
– 42、查询每门功成绩最好的前两名
– 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
– 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
<span class="token keyword">select</span> s_birth<span class="token punctuation">,</span><span class="token punctuation">(</span>DATE_FORMAT<span class="token punctuation">(</span><span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token string">'%Y'</span><span class="token punctuation">)</span><span class="token operator">-</span>DATE_FORMAT<span class="token punctuation">(</span>s_birth<span class="token punctuation">,</span><span class="token string">'%Y'</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token punctuation">(</span><span class="token keyword">case</span> <span class="token keyword">when</span> DATE_FORMAT<span class="token punctuation">(</span><span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token string">'%m%d'</span><span class="token punctuation">)</span><span class="token operator">></span>DATE_FORMAT<span class="token punctuation">(</span>s_birth<span class="token punctuation">,</span><span class="token string">'%m%d'</span><span class="token punctuation">)</span> <span class="token keyword">then</span> <span class="token number">0</span> <span class="token keyword">else</span> <span class="token number">1</span> <span class="token keyword">end</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">as</span> age <span class="token keyword">from</span> student<span class="token punctuation">;</span>
– 47、查询本周过生日的学生
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’))
<span class="token keyword">select</span> WEEK<span class="token punctuation">(</span>DATE_FORMAT<span class="token punctuation">(</span><span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token string">'%Y%m%d'</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
– 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)
– 49、查询本月过生日的学生
<span class="token keyword">select</span> <span class="token operator">*</span> <span class="token keyword">from</span> student <span class="token keyword">where</span> <span class="token keyword">MONTH</span><span class="token punctuation">(</span>DATE_FORMAT<span class="token punctuation">(</span><span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token string">'%Y%m%d'</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">=</span><span class="token keyword">MONTH</span><span class="token punctuation">(</span>s_birth<span class="token punctuation">)</span>
– 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)
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