thinkphp初学者教程：一对多模型关联

terry 2年前 (2023-09-24) 阅读数 58 #后端开发

1.前言

上一节介绍了如何使用一对一的模型将教师信息链接到课程列表。本节介绍如何在学生课程关联列表中使用一对多模型。关联学生选课信息，一对多模型关联主要是针对查询具有一对多关系的两张表，联表查询会带来性能问题。 ThinkPHP提供了()方法用于预加载此类链表查询。当一对多模型关联时，框架底层会使用主驱动表的id集合到另一个表 IN查询取所有数据在一次即可自动对应。这种操作减少了开发人员编写大量循环和数据处理代码的需要。？ SQL添加学生表数据如下：如下图： L♿ 添加学生课程语句如下：如下图所示：

`3. 定义路由`

这里复用了上一节的控制器。只需要为学生排班列表定义一条路线：

//学生课程表关联列表接口
Route::get('course-students','app\controller\Study\CourseController@courseStudnetList');

代码块如下图：
 
4。方法定义 
    /**
     * 学生课表信息关联表
     * @return \think\response\Json
     */
    public function courseStudnetList(){
        //每页条数
        $size = (int)$this->request->param('size', 15);

        $courseStudents = StudentModel::order('created_at DESC')
            ->with('course_students')
            ->paginate($size);

        return json($courseStudents);
    }
 代码块  如下图所示： 
 
5.在中指定一对多模型关联方法
，StudentModel

可以在课程中定义学生代码方法：
6。通过模型关联请求数据

使用如下 postman请求接口数据如下：

{
    "total": 14,
    "per_page": 10,
    "current_page": 1,
    "last_page": 2,
    "data": [
        {
            "id": 1,
            "name": "赵雷",
            "age": 24,
            "id_number": "42011720100506XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 1,
                    "student_id": 1,
                    "course_id": 1,
                    "created_at": 1603617951
                },
                {
                    "id": 2,
                    "student_id": 1,
                    "course_id": 2,
                    "created_at": 1603617951
                },
                {
                    "id": 3,
                    "student_id": 1,
                    "course_id": 2,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 2,
            "name": "孙空",
            "age": 23,
            "id_number": "42011720110606XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 4,
                    "student_id": 2,
                    "course_id": 3,
                    "created_at": 1603617951
                },
                {
                    "id": 5,
                    "student_id": 2,
                    "course_id": 4,
                    "created_at": 1603617951
                },
                {
                    "id": 6,
                    "student_id": 2,
                    "course_id": 6,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 3,
            "name": "钱学",
            "age": 18,
            "id_number": "42011720120306XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 7,
                    "student_id": 3,
                    "course_id": 4,
                    "created_at": 1603617951
                },
                {
                    "id": 8,
                    "student_id": 3,
                    "course_id": 1,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 4,
            "name": "王五",
            "age": 25,
            "id_number": "42011720030506XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 9,
                    "student_id": 4,
                    "course_id": 1,
                    "created_at": 1603617951
                },
                {
                    "id": 10,
                    "student_id": 4,
                    "course_id": 3,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 5,
            "name": "张红",
            "age": 19,
            "id_number": "42011720050506XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 11,
                    "student_id": 5,
                    "course_id": 5,
                    "created_at": 1603617951
                },
                {
                    "id": 12,
                    "student_id": 5,
                    "course_id": 6,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 6,
            "name": "吴晓明",
            "age": 21,
            "id_number": "42011720040506XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 13,
                    "student_id": 6,
                    "course_id": 4,
                    "created_at": 1603617951
                },
                {
                    "id": 14,
                    "student_id": 6,
                    "course_id": 2,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 7,
            "name": "李珍",
            "age": 25,
            "id_number": "42011720060206XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [
                {
                    "id": 15,
                    "student_id": 7,
                    "course_id": 3,
                    "created_at": 1603617951
                },
                {
                    "id": 16,
                    "student_id": 7,
                    "course_id": 4,
                    "created_at": 1603617951
                }
            ],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 8,
            "name": "猪刚",
            "age": 22,
            "id_number": "42011720070806XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 9,
            "name": "李亮",
            "age": 26,
            "id_number": "42011720080906XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [],
            "created_at_text": "2020-10-25 17:25"
        },
        {
            "id": 10,
            "name": "周康",
            "age": 28,
            "id_number": "42011720000706XXXX",
            "created_at": 1603617951,
            "update_at": 0,
            "status": 1,
            "course_students": [],
            "created_at_text": "2020-10-25 17:25"
        }
    ]
}

代码块

如下图：。总结

本节主要介绍一对多模型关联。使用with预加载的底层实现是IN查询，因此无需担心循环搜索问题。此外，如果您需要继续链接上述结果中的课程信息，您可以使用 和 关闭查询，如下所示：

    /**
     * 学生课表信息关联表
     * @return \think\response\Json
     */
    public function courseStudnetList(){
        //每页条数
        $size = (int)$this->request->param('size', 15);

        $courseStudents = StudentModel::order('created_at DESC')
            ->with(['course_students' => function($query){
                $query->with('course');
            }])
            ->paginate($size);

        return json($courseStudents);
    }

代码块

，您需要在其中创建新的 课程在 CourseStudentModel 模型 一对一相关的课程信息。

提示：代码存储库：https://gitee.com/love-for-poetry/tp6