php - 解析表(mysql, php)

Question

我有 3 个表，分别称为 class 、 student 和 class_student(resolving table) 。这是由于类(class)和学生之间的多对多关系。一个学生可以有多个类(class)，一个类(class)可以有多个学生。类里面的字段是(class_id，class_start_time和class_end_time)，student(student_id，student_name，student_age)，class_student(student_id，class_id)。我的问题是:在类(class)内，它包括学生，如何将学生添加到类(class)表中？还是应该使用解析表？我对解析表的理解很薄弱，我不确定它的目的是什么。

谢谢大家的回答!

当我向 class student 表添加一条新记录时，是否也向 class 表添加一条新记录？

Answer 1

解决多对多关系的最常见方法是通过单独的关系表(如 Barmar 所述)。

在您的情况下，该表可能包含以下字段:

table class_students
--------------------
id      // an unique id of that relationship; 
        // could be ommitted, could be an autoincrement, 
        // could also be a "handcrafted" id like classid_userid -> 21_13 (I need this kind of id's for an ember-api. 
        // All depending on your needs
class   // the id of the related class
student   // the id of the related student
// maybe add additional fields:
type     // to describe that relationship
sort     

然后你会得到一个特定类(class)的所有学生:

$class_id = 1;
$sql = "Select * from students, class_students where students.id=class_students.student AND class_student.class=".$class_id;
// note, that you should do that via prepared statements, 
// this is only for simplicity to show how to proceed.