MySQL經典練手面試題

建立數據庫

表和字段java

1.學生表 
Student(s_id,s_name,s_birth,s_sex) –學生編號,學生姓名, 出生年月,學生性別 sql

2.課程表 
Course(c_id,c_name,t_id) – –課程編號, 課程名稱, 教師編號數據庫

3.教師表
Teacher(t_id,t_name) –教師編號,教師姓名測試

4.成績表 
Score(s_id,c_id,s_score) –學生編號,課程編號,分數spa

測試數據3d

--學生表
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`(
    `s_id` VARCHAR(20),
    `s_name` VARCHAR(20) NOT NULL comment '姓名',
    `s_birth` VARCHAR(20) NOT NULL comment '生日',
    `s_sex` VARCHAR(10) NOT NULL comment '性別',
    PRIMARY KEY(`s_id`)
);
--課程表
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`(
    `c_id`  VARCHAR(20),
    `c_name` VARCHAR(20) NOT NULL comment '課程名',
    `t_id` VARCHAR(20) NOT NULL comment '學生id',
    PRIMARY KEY(`c_id`)
);
--教師表
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher`(
    `t_id` VARCHAR(20),
    `t_name` VARCHAR(20) NOT NULL comment '教師名稱',
    PRIMARY KEY(`t_id`)
);
--成績表
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score`(
    `s_id` VARCHAR(20),
    `c_id`  VARCHAR(20) NOT NULL comment '課程名',
    `s_score` INT(3) NOT NULL comment '成績',
    PRIMARY KEY(`s_id`,`c_id`)
);
--插入學生表測試數據
insert into student values('01' , '趙雷' , '1990-01-01' , '男');
insert into student values('02' , '錢電' , '1990-12-21' , '男');
insert into student values('03' , '孫風' , '1990-05-20' , '男');
insert into student values('04' , '李雲' , '1990-08-06' , '男');
insert into student values('05' , '周梅' , '1991-12-01' , '女');
insert into student values('06' , '吳蘭' , '1992-03-01' , '女');
insert into student values('07' , '鄭竹' , '1989-07-01' , '女');
insert into student values('08' , '王菊' , '1990-01-20' , '女');
--課程表測試數據
insert into course values('01' , '語文' , '02');
insert into course values('02' , '數學' , '01');
insert into course values('03' , '英語' , '03');
 
--教師表測試數據
insert into teacher values('01' , '張三');
insert into teacher values('02' , '李四');
insert into teacher values('03' , '王五');
 
--成績表測試數據
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);

練習題和sql實現語句

一、查詢"01"課程比"02"課程成績高的學生的信息及課程分數code

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' 
where b.s_score>c.s_score blog

查詢結果:數學

二、查詢"01"課程比"02"課程成績低的學生的信息及課程分數class

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' 
where b.s_score<c.s_score 

查詢結果:

三、查詢平均成績大於等於60分的同窗的學生編號和學生姓名和平均成績

select a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score 
from student a join score b on a.s_id=b.s_id
group by a.s_id,a.s_name having round(avg(b.s_score),2)>=60;

查詢結果:

四、查詢平均成績小於60分的同窗的學生編號和學生姓名和平均成績-- (包括有成績的和無成績的)

select a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score 
from student a join score b on a.s_id=b.s_id
group by a.s_id,a.s_name having round(avg(b.s_score),2)<60;

查詢結果:

五、查詢全部同窗的學生編號、學生姓名、選課總數、全部課程的總成績

select a.s_id as '學生編號',a.s_name as '學生姓名',
sum(b.c_id) as '選課總數',
sum(b.s_score) as '課程總成績'
from student a join score b on a.s_id=b.s_id
GROUP BY a.s_id,a.s_name

查詢結果:

六、查詢"李"姓老師的數量

select count(t_id) as '老師數量'
from teacher 
where t_name LIKE '李%';

查詢結果:

七、查詢學過"張三"老師授課的同窗的信息

select a.* from 
    student a join score s on a.s_id = s.s_id 
    where s.c_id in(
        select c_id from course where t_id = (
            select t_id from teacher where t_name='張三'));

查詢結果:沒有符合結果

八、查詢沒學過"張三"老師授課的同窗的信息

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 c_id from course where t_id =(
                select t_id from teacher where t_name = '張三')));

查詢結果:

九、查詢學過編號爲"01"而且也學過編號爲"02"的課程的同窗的信息

十、查詢學過編號爲"01"可是沒有學過編號爲"02"的課程的同窗的信息

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