愛因詩賢 ·一對多模型關聯
1.前言
前面小節介紹了如何在課程列表中使用一對一模型關聯出教師信息，本小節介紹如何在學生課程關聯列表中一對多關聯出學生選課信息，一對多模型關聯主要針對的是查詢兩個表有一對多的關系，而連表查詢就可能帶來性能問題， ThinkPHP中提供了 with()方法用于這種連表查詢的預加載，在一對多模型關聯的時候，框架底層會用過主驅動表的 id 集去另外一張表中 IN 查詢一次獲取全部數據并且能自動對應，這樣的操作就減少了開發者書寫很多循環和處理數據的代碼了。
2.添加測試數據
這里為了演示方便，需要向之前新建好的 學生表(student)、學生課程關聯表(student_course) 添加數據，添加學生表數據的 SQL 如下：
如下圖所示：
添加學生課程關聯表數據 SQL 語句如下：
如下圖所示：
3.定義路由
這里復用上小節的控制器，只需要定義一個學生課表關列表的路由：
//學生課程表關聯列表接口
Route::get('course-students','app\controller\Study\CourseController@courseStudnetList');
如下圖所示：
4.方法定義
/**
* 學生課表信息關聯表
* @return \think\response\Json
*/
public function courseStudnetList(){
//每頁條數
$size = (int)$this->request->param('size', 15);
$courseStudents = StudentModel::order('created_at DESC')
->with('course_students')
->paginate($size);
return json($courseStudents);
}
如下圖所示：
5.設置一對多模型關聯方法
在 StudentModel 中可以定義 courseStudents 方法：
/**
* 一對多模型關聯
* @return \think\model\relation\HasMany
*/
public function courseStudents(){
return $this->hasMany(StudentCourseModel::class,"student_id","id");
}
如下圖所示：
6.請求模型關聯之后的數據
下面使用 postman 請求接口數據如下：
{
"total": 14,
"per_page": 10,
"current_page": 1,
"last_page": 2,
"data": [
{
"id": 1,
"name": "趙雷",
"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": "孫空",
"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": "錢學",
"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": "張紅",
"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": "吳曉明",
"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": "豬剛",
"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"
}
]
}
如下圖所示：
7.小結
本小節主要介紹了一對多模型關聯，其中使用 with 預加載底層實現是 IN 查詢一次性查出來的，所以無需擔心存在循環查詢的問題，另外如需要在上述結果中繼續關聯出課程信息可以如下使用 with 閉包查詢：
/**
* 學生課表信息關聯表
* @return \think\response\Json
*/
public function courseStudnetList(){
//每頁條數
$size = (int)$this->request->param('size', 15);
$courseStudents = StudentModel::order('created_at DESC')
->with(['course_students' => function($query){
$query->with('course');
}])
->paginate($size);
return json($courseStudents);
}
其中需要在 CourseStudentModel 模型中新建 course 一對一關聯課程信息。
Tips： 代碼倉庫：https://gitee.com/love-for-poetry/tp6
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