建資料庫students (建立三個** 分別儲存學生，教師，課程資訊)
mysql->create table student
->(
->key_student int(5) not null auto_increment, student_name varchar(20) not null,primary key (key_student)
->);
mysql->create table teacher
->（key_teacher int(5) not null auto_increment,teacher_name varhcar(20) not null,primary key (key_teacher)
->);
mysql->create table course ( key_course int(5) not null auto_increment,key_student int(5) not null,key_teacher int(5) not null,course_name varchar(20) not null,primary key (key_course)
->);
向三個**新增資料
mysql->insert into student (student_name) values (『tom』);
mysql->insert into student (student_name) values (『mary』);
mysql->insert into student (student_name) values (『bob』);
mysql->insert into teacher (teacher_name) values (『thomas yang』);
mysql->insert into teacher (teacher_name) values (『jonna farmer』);
mysql->insert into teacher (teacher_name) values (『christ miller』);
mysql->insert into course (course_name,key_student,key_teacher) values (『mathematics』,2,1);
mysql->insert into course (course_name,key_student,key_teacher) values (『physics』,1,3);
mysql->insert into course (course_name,key_student,key_teacher) values (『physics』,4,2);
insert into course (course_name,key_student,key_teacher) values (『biology』,3,4);
通過表的關聯來查詢資訊，例：列出所有課程的任課教師及選修該課的學生：
mysql->select course.course_name,teacher.teacher_name,student.student_namefrom course,teacher,student where course.key_student=student.key_student and course.key_teacher=teacher.key_teacher;
可以把上表通過關聯生成的虛擬表，虛擬表通過where子句將三個不同的**連線在一起
mysql->select
->course.course_name, teacher.teacher_name
->from course,teacher;
mysql->select
->course.course_name, teacher.teacher_name
->from course,teacher where course.key_teacher=teacher.key_teacher;
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