一个对inner jion ...on 的sql多表联合查询的练习

Posted 2021-01-01 胡叔叔

create database practiceSql;

use practiceSql;
--
create table student(
    `id` bigint not null auto_increment comment ‘主键id自增‘,
    `name` varchar(20) not null comment ‘学生名‘,
    `student_num` int not null comment ‘学号‘,
    `sex` varchar(4) not null comment ‘性别‘,
    `age` int not null comment ‘年龄‘,
    `college` varchar(50) not null comment‘学院‘,
    primary key(id),
    key idx_name(name),
    key idx_student_num(student_num),
    key idx_college (college)
    )engine=InnoDB Auto_increment=1000 default charset=utf8 comment=‘学生表‘;


--插入10个学生信息
insert into student(name,student_num,sex,age,college)
    values (‘张三‘,‘1‘,‘男‘,‘20‘,‘计算机学院‘),
           (‘李红‘,‘2‘,‘女‘,‘21‘,‘计算机学院‘),
           (‘黄山‘,‘3‘,‘男‘,‘20‘,‘美术学院‘),
           (‘李丽‘,‘4‘,‘女‘,‘22‘,‘美术学院‘),
           (‘何冲‘,‘5‘,‘男‘,‘20‘,‘计算机学院‘),
           (‘欧皇‘,‘6‘,‘男‘,‘21‘,‘英语学院‘),
           (‘马涛‘,‘7‘,‘女‘,‘19‘,‘英语学院‘),
           (‘廖彤‘,‘8‘,‘女‘,‘20‘,‘计算机学院‘);
           
           
--课程表
create table course (
    `course_id` bigint not null auto_increment comment‘课程id‘,
    `student_num` int not null comment‘学号‘,
    `student_name` varchar(20) not null comment‘姓名‘,
    `name` varchar(50) not null comment ‘课程名字‘,
    primary key(course_id),
    key idx_student_num(student_num),
    key idx_student_name(student_name)
) engine=innoDB auto_increment=100 default charset=utf8 comment=‘课程表‘;


--向课程表插入信息

insert into course(student_num,student_name,name)
        values (1,‘张三‘,‘数学‘),
                (2,‘李红‘,‘英语‘),
                (1,‘张三‘,‘英语‘),
                (1,‘张三‘,‘数学‘),
                (2,‘李红‘,‘语文‘),
                (1,‘张三‘,‘数学‘),
                (3,‘黄山‘,‘语文‘);
                
                
--教师表
create table teacher(
    `teacher_id` bigint not null auto_increment comment‘教师id‘,
    `name` varchar (20) not null comment‘教师名字‘,
    `sex` varchar(4) not null comment ‘性别‘,
    `age` int not null comment ‘年龄‘,
    `course` varchar (50) not null comment ‘所教科目‘,
    primary key(teacher_id),
    key idx_name(name),
    key idx_course(course)
) engine=innoDB auto_increment=200 default charset=utf8 comment=‘教师表‘;

--设置主键自增
alter table teacher change teacher_id teacher_id bigint not null  auto_increment;

insert into teacher(name,sex,age,course) values
                    (‘Mr.Lee‘,‘男‘,40,‘数学‘),
                    (‘Mr.Hu‘,‘女‘,33,‘英语‘),
                    (‘Mr.Chen‘,‘男‘,38,‘语文‘);
                    
--查询张三的所有信息 课程名字，课程的老师
--这个不行
select distinct  id , student.name as sname,student.student_num as snum,student.sex as ssex,student.age as sage,college 
        ,course.name as cname,teacher.name as tname from student,teacher,course where student.name=‘张三‘;
        
        --这个也不行
        select distinct  id , student.name as sname,student.student_num as snum,student.sex as ssex,student.age as sage,college 
        ,course.name as cname,teacher.name as tname from student,teacher,course where course.student_name=‘张三‘;

        --这个可以
        select  distinct id , s.name as sname,s.student_num as snum,s.sex as ssex,s.age as sage,college 
        ,c.name as cname,t.name as tname from ((student s inner join course c on c.student_name = s.name )
                                                                    inner join teacher t on  t.course=c.name) 
        where s.name =‘张三‘;
        --没有distinct
            select  id , s.name as sname,s.student_num as snum,s.sex as ssex,s.age as sage,college 
        ,c.name as cname,t.name as tname from ((student s inner join course c on c.student_name = s.name )
                                                                    inner join teacher t on  t.course=c.name) 
        where s.name =‘张三‘;
        
--查询张三的所有信息 课程名字，
        
        select distinct  id , s.name as sname,s.student_num as snum,s.sex as ssex,s.age as sage,college 
        ,c.name as cname from student s inner join course c on c.student_name = s.name
                                                                    
        where s.name =‘张三‘;
        --更新老师课程
        update teacher set course = "数学" where course =‘数学老师‘ ;