mysql笔试题写sql语句_sql面试题50题（mysql版）

「爱情、让人受尽委屈。」 2023-01-11 01:23 118阅读 0赞

表名和字段

\--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 c.\*,a.s\_score as 01课程score,b.s\_score as 02课程score from

score a,score b

left join student c

on b.s\_id = c.s\_id

where a.s\_id = b.s\_id and a.c\_id = '01' and b.c\_id = '02' and a.s\_score > b.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课程,c.s\_score as 02课程 from student a

join score b

on a.s\_id=b.s\_id and b.c\_id = '01'

left join score c

on b.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 a.s\_id,a.s\_name,round(avg(b.s\_score),2) as 平均成绩 from student a

join score b

on a.s\_id = b.s\_id

group by b.s\_id having 平均成绩 >= 60;

备注：round\[avg(成绩),1\]里,round是四舍五入函数，1代表保留1位小数

\-- 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.,round(avg(a.s\_score),2) as 平均成绩 from

student b

left join score a on b.s\_id = a.s\_id group by a.s\_id having 平均成绩 < 60

union

select b.,0 as 平衡成绩 from student b where b.s\_id not in (select 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 选课总数 ,sum(b.s\_score) as 总分 from student a

left join score b

on a.s\_id = b.s\_id group by s\_id ;

\-- 6、查询"李"姓老师的数量

select count(\*) as 李姓老师数量 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.c\_id from course c

join teacher d on c.t\_id = d.t\_id where d.t\_name = '张三');

\-- 8、查询没学过"张三"老师授课的同学的信息

select a.\* from student a left join score b on a.s\_id = b.s\_id 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 a.s\_id;

\-- 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 \* from student where s\_id in

(select a.s\_id from score a join score b on a.s\_id = b.s\_id

where a.c\_id = '01' and b.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 \* 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' );

\-- 11、查询没有学全所有课程的同学的信息

select \* from student where s\_id not in

(select s\_id from score group by s\_id having count(c\_id) = 3);

\-- 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 distinct a.\* from student a left join score b

on a.s\_id = b.s\_id where b.c\_id in

(select c\_id from score where s\_id = '01') and a.s\_id != '01' ;

注意：distinct是去重的

\-- 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 group by s\_id having count(c\_id) =

(select count(c\_id) from score where s\_id = '01') and s\_id not in

(select s\_id from score where c\_id not in

(select c\_id from score where s\_id = '01')) and 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 in

(select c\_id from course where t\_id in

(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 ,b.s\_name,round(avg(a.s\_score),2) as 平均成绩 from score a

left join student b on a.s\_id = b.s\_id

where s\_score < 60 group by s\_id having count(1) >=2;

或者试试

select a.s\_id ,b.s\_name,round(avg(a.s\_score),2) as 平均成绩 from score a

left join student b on a.s\_id = b.s\_id

where a.s\_score < 60 group by a.s\_id having count(\*) >=2;

\-- 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

left join score b on a.s\_id = b.s\_id

where 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\_name ,

sum(case when b.c\_id = '01' then s\_score else null end ) as 语文,

sum(case when b.c\_id = '02' then s\_score else null end ) as 数学,

sum(case when b.c\_id = '03' then s\_score else null end ) as 英语,

round(avg(s\_score),2) as 平均成绩

from student a left join score b on a.s\_id = b.s\_id group by a.s\_name

order by 平均成绩 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 b.c\_id,b.c\_name,

max(a.s\_score) as 最高分,

min(a.s\_score) as 最低分,

round(avg(a.s\_score),2) as 平均分,

round(sum(case when a.s\_score>= 60 then 1 else 0 end)/count(s\_id),2) as 及格率 ,

round(sum(case when a.s\_score>= 70 and a.s\_score <80 then 1 else 0 end)/count(s\_id),2) as 中等率,

round(sum(case when a.s\_score>= 80 and a.s\_score <90 then 1 else 0 end)/count(s\_id),2) as 优良率,

round(sum(case when a.s\_score>= 90 then 1 else 0 end)/count(s\_id),2) as 优秀率

from score a

left join course b

on a.c\_id = b.c\_id group by b.c\_id;

\-- 19、按各科成绩进行排序，并显示排名

第一种：

set @pre\_c\_id:= '01';

set @rank:=0;

select tb2.s\_id ,tb2.c\_id,tb2.s\_score,tb2.排名 from

(select \*,(case when tb1.c\_id = @pre\_c\_id then @rank:=@rank+1 else @rank:=1 end) as 排名,

(case when @pre\_c\_id = tb1.c\_id then @pre\_c\_id else @pre\_c\_id:=tb1.c\_id end ) as pre\_c\_id

from

(select \* from score order by c\_id,s\_score desc) tb1 )tb2;

如果看不懂用第二种方法：

SELECT a.c\_id,a.s\_id,a.s\_score,COUNT(b.s\_score)+1 AS 排名

FROM score a LEFT JOIN score b ON a.s\_score

GROUP BY a.c\_id,a.s\_id,a.s\_score ORDER BY a.c\_id,排名,a.s\_id ASC

\-- 20、查询学生的总成绩并进行排名

set @rank:=0;

select \* ,(@rank:=@rank+1) as rank from

(select s\_id ,sum(s\_score) as 总成绩 from score

group by s\_id order by 总成绩 desc) tb1;

\-- 21、查询不同老师所教不同课程平均分从高到低显示

select a.c\_id, d.t\_name,round(avg(a.s\_score)) as 平均分 from score a

left join student b on a.s\_id = b.s\_id

left join course c on a.c\_id = c.c\_id

left join teacher d on c.t\_id = d.t\_id group by a.c\_id

order by 平均分 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

set @pre\_c\_id:= '01';

set @rank:=0;

select b.s\_name,tb2.s\_id ,tb2.c\_id,tb2.s\_score,tb2.排名 from

(select \*,(case when tb1.c\_id = @pre\_c\_id then @rank:=@rank+1 else @rank:=1 end) as 排名,

(case when @pre\_c\_id = tb1.c\_id then @pre\_c\_id else @pre\_c\_id:=tb1.c\_id end ) as pre\_c\_id

from

(select \* from score order by c\_id,s\_score desc) tb1 )tb2 join student b on tb2.s\_id = b.s\_id where 排名 = 2 or 排名 =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 b.c\_id,b.c\_name ,

sum(case when a.s\_score >=85 then 1 else 0 end) as 100-85,

concat(round(100sum(case when a.s\_score >=85 then 1 else 0 end)/count(),2), '%') as 百分比,

sum(case when a.s\_score <85 and a.s\_score >=70 then 1 else 0 end) as 85-70,

concat(round(100sum(case when a.s\_score <85 and a.s\_score >=70 then 1 else 0 end)/count(),2),'%') as 百分比,

sum(case when a.s\_score <70 and a.s\_score >=60 then 1 else 0 end) as 70-60,

concat(round(100sum(case when a.s\_score <70 and a.s\_score >=60 then 1 else 0 end)/count(),2) ,'%')as 百分比,

sum(case when a.s\_score <60 and a.s\_score >=0 then 1 else 0 end) as 60-0,

concat(round(100sum(case when a.s\_score <60 and a.s\_score >=0 then 1

else 0 end)/count(),2),'%') as 百分比

from score a left join course b on a.c\_id = b.c\_id group by b.c\_id;

\-- 24、查询学生平均成绩及其名次

select tb1.\*,(@rank:=@rank +1 ) as rank from

(select s\_id ,round(avg(s\_score),2) as 平均成绩 from score

group by s\_id order by 平均成绩 desc) tb1,(select @rank:=0) b;

\-- 25、查询各科成绩前三名的记录

set @pre\_c\_id:= '01';

set @rank:=0;

select b.s\_name,tb2.s\_id ,tb2.c\_id,tb2.s\_score,tb2.排名 from

(select \*,(case when tb1.c\_id = @pre\_c\_id then @rank:=@rank+1 else @rank:=1 end) as 排名,

(case when @pre\_c\_id = tb1.c\_id then @pre\_c\_id else @pre\_c\_id:=tb1.c\_id end ) as pre\_c\_id

from

(select \* from score order by c\_id,s\_score desc) tb1 )tb2 join student b on tb2.s\_id = b.s\_id where 排名 <4;

\-- 26、查询每门课程被选修的学生数

select c\_id ,count(s\_id) as 选修人数 from score 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 a.s\_id ,b.s\_name from score a left join student b on a.s\_id = b.s\_id group by s\_id having count(\*) = 2;

\-- 28、查询男生、女生人数

select sum(case s\_sex when '男' then 1 else 0 end) as 男生人数,

sum(case s\_sex when '女' then 1 else 0 end) as 女生人数 from student;

\-- 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

\--略，不想写

\-- 31、查询1990年出生的学生名单

select \* 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 平均成绩 from score group by c\_id order by 平均成绩 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(s\_score),2) as 平均成绩 from score a

left join student b on a.s\_id = b.s\_id group by a.s\_id having 平均成绩>=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 b.s\_name ,a.s\_score from score a

left join student b on a.s\_id = b.s\_id

where a.c\_id=(select c\_id from course where c\_name = '数学')and a.s\_score < 60;

\-- 35、查询所有学生的课程及分数情况；

select b.s\_name,

sum(case when a.c\_id = '01' then a.s\_score else null end) as 语文,

sum(case when a.c\_id = '02' then a.s\_score else null end) as 数学,

sum(case when a.c\_id = '03' then a.s\_score else null end) as 英语

from score a right join student b on a.s\_id = b.s\_id group by b.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 b.s\_name,

sum(case when a.c\_id = '01' then a.s\_score else null end) as 语文,

sum(case when a.c\_id = '02' then a.s\_score else null end) as 数学,

sum(case when a.c\_id = '03' then a.s\_score else null end) as 英语

from score a right join student b on a.s\_id = b.s\_id group by b.s\_name having 语文>= 70 or 数学>= 70 or 英语>= 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 c\_id,count(\*) as 学生人数 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

select a.\*,b.c\_id,max(b.s\_score) as 最高成绩 from student a

right join score b on a.s\_id = b.s\_id

group by b.c\_id

having b.c\_id = (select c\_id from course

where t\_id = (select t\_id from teacher where t\_name = '张三'));

\-- 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

\--(这题我搞不清题目是什么意思,是指查找学生个体参加了的所有课程的成绩各不相同的那个学生信息呢？还是所有课程之间做对比呢，我更倾向于理解为前者)

\--理解为前者的写法

select \* from

(select \* from score group by s\_id,s\_score) tb1

group by s\_id having count(\*) = 1;

\--理解为后者的写法

select distinct a.s\_id,a.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、查询每门课程成绩最好的前两名

set @pre\_c\_id:= '01';

set @rank:=0;

select tb2.s\_id ,tb2.c\_id,tb2.s\_score from

(select \*,(case when tb1.c\_id = @pre\_c\_id then @rank:=@rank+1 else @rank:=1 end) as 排名,

(case when @pre\_c\_id = tb1.c\_id then @pre\_c\_id else @pre\_c\_id:=tb1.c\_id end ) as pre\_c\_id

from

(select \* from score order by c\_id,s\_score desc) tb1 )tb2

join student b on tb2.s\_id = b.s\_id where 排名 <3;

\-- 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，若人相同，按课程号升序排列

select c\_id ,count(\*) as 选修人数 from score group by c\_id having 选修人数>5 order by 选修人数 desc , c\_id asc;

\-- 44、检索至少选修两门课程的学生学号

select s\_id from score group by s\_id having count(\*) >= 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(\*) = 3)

\--46、查询各学生的年龄

select s\_name ,(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

\---(实现得并不完全，因为例如出生月日为‘01-01’在每一年可能会输入不同周)

select \* from student where week(date\_format(s\_birth,'%m%d'))=week(date\_format(now(),'%m%d')) ;

\-- 48、查询下周过生日的学生

select \* from student

where week(date\_format(s\_birth,'%m%d'))=week(date\_format(date\_add(now(),interval 7-dayofweek(now())+1 day),'%m%d'));

\-- 49、查询本月过生日的学生

select \* from student where date\_format(s\_birth,'%m') = date\_format(now(),'%m')

\-- 50、查询下月过生日的学生

select \* from student where date\_format(s\_birth,'%m') = date\_format(date\_add(now(),interval 1 month),'%m')

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