如何通过模型关系从三个相关表中获取数据？

Posted 2023-02-16

【中文标题】如何通过模型关系从三个相关表中获取数据？

【英文标题】：How to get data from three related table with it's model relationships?

【发布时间】：2021-08-05 04:30:34

【问题描述】：

我有三个这样的表：

费用：-

expense_id user_id

用户：-

user_id employee_id

员工：-

employee_id 名字 姓氏

我想从expense.user_id = user.user_id 的员工表中获取first_name 和 last_name，我尝试了类似下面的方法，但我没有得到正确的数据。

费用模式：-

 public function users()

    return $this->hasOne(User::class,'user_id','user_id');

用户模型：-

public function employee()
    return $this->hasOne(Employee::class,'employee_id','user_id');

和员工模型：-

public function users()

    return $this->belongsTo(User::class,'employee_id');

我打电话是这样看的：-

<td>$expense->users->employee->first_name ." " . $expense->users->employee->last_name </td>

它显示数据，但不是预期的数据。

我的错误在哪里，应该怎么做？ 请帮忙！ 谢谢！

【参考方案1】：

我建议你用这种方式重新设计你的数据库和关系：

Expense:-

id
user_id

User:-

id

Employee:-

id
user_id
first_name
last_name

对于BelongsTo 和HasOne 关系，请使用单名词：

class Expense extends Model

    public function user()
    
        return $this->belongsTo(User::class);
    


class User extends Model

    public function employee()
    
        return $this->hasOne(Employee::class);
    


class Employee extends Model

    public function user()
    
        return $this->belongsTo(User::class);
    

    public function getFullNameAttribute()
    
        return $this->first_name . ' ' . $this->last_name;
    

最后，您可以像这样访问员工的全名：

$expense->user->employee->full_name;

【讨论】：

我无法编辑我的数据库，因为我从员工中选择了用户，在这里我声明谁可以访问系统

如果这段代码不是根据重新设计的数据库，所以这不起作用，也没有错误，但如果是根据你的建议，我应该另找方法。

@ZiaYamin 我已经添加了另一个答案，请检查。

【参考方案2】：

class Expense extends Model

    public function user()
    
        return $this->belongsTo(User::class);
    


class User extends Model

    public function employee()
    
        return $this->belongsTo(Employee::class);
    


class Employee extends Model

    public function user()
    
        return $this->hasOne(User::class);
    

    public function getFullNameAttribute()
    
        return $this->first_name . ' ' . $this->last_name;
    

然后访问客户属性：

<td>$expense->user->employee->full_name</td>

【讨论】：

我应该在哪里返回这个return $expense->user->employee->full_name;

@ZiaYamin 在你的 html 中，我已经更新了我的答案。

不带任何数据

@ZiaYamin 啊，我错过了return 方法中的getFullNameAttribute 关键字。我已经更新了我的答案，请再试一次。

我添加了 return 关键字，但注意到改变了

【参考方案3】：

我相信你在滥用雄辩的关系。

One To One Relationship.

One To Many Relationship

一对多关系用于定义一个关系 单个模型是一个或多个子模型的父模型。

试试这个吧。

use App\Models\Employee;
use App\Models\Expense;

// User model.
class User extends Authenticatable

    use HasFactory, Notifiable;

    protected $primaryKey = 'user_id';

    protected $table = 'users';

    public function employee()
    
        return $this->hasOne(Employee::class, "employee_id", "employee_id");
    

    public function expenses()
    
        return $this->hasMany(Expense::class, "user_id", "user_id");
    
    

// Expense model
class Expense extends Model

    use HasFactory;

    protected $primaryKey = 'expense_id';

    public function user()
    
        return $this->belongsTo(User::class, "user_id", "user_id");
    

// Employee model.
class Employee extends Model

    use HasFactory;

    protected $primaryKey = 'employee_id';

    public function user()
    
        return $this->belongsTo(User::class, "employee_id", "employee_id");
    

// 'create_users_table' migration.
class CreateUsersTable extends Migration

    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    
        Schema::create('users', function (Blueprint $table) 
            $table->id('user_id');
            $table->unsignedBigInteger("employee_id");
            $table->timestamps();

            $table->foreign("employee_id")
                ->references("employee_id")
                ->on("employees")
                ->onDelete("cascade");
        );
    

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    
        Schema::dropIfExists('users');
    

// 'create_expenses_table' migration.
class CreateExpensesTable extends Migration

    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    
        Schema::create('expenses', function (Blueprint $table) 
            $table->id('expense_id');
            $table->unsignedBigInteger("user_id");
            $table->timestamps();

            $table->foreign("user_id")
                ->references("user_id")
                ->on("users")
                ->onDelete("cascade");

        );
    

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    
        Schema::dropIfExists('expenses');
    

// 'create_employees_table' migration.
class CreateEmployeesTable extends Migration

    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    
        Schema::create('employees', function (Blueprint $table) 
            $table->id("employee_id");
            $table->string("first_name");
            $table->string("last_name");
            $table->timestamps();
        );
    

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    
        Schema::dropIfExists('employees');
    

// Sample query 1.
App\Models\Expense::find(1)
    ->with(
        ["user" => function($query)
        
            $query->with("employee");
        ])
    ->first();

// Sample output 1.
/*
=> App\Models\Expense #4172
     expense_id: 1,
     user_id: 1,
     created_at: null,
     updated_at: null,
     user: App\Models\User #4322
       user_id: 1,
       employee_id: 1,
       created_at: null,
       updated_at: null,
       employee: App\Models\Employee #4330
         employee_id: 1,
         first_name: "john",
         last_name: "doe",
         created_at: null,
         updated_at: null,
       ,
     ,
   

*/

// Sample query 2.
App\Models\Expense::with(
    ["user" => function($query)
    $query->with("employee");
    ])->get();

// Sample output 2.
/*
=> Illuminate\Database\Eloquent\Collection #4318
     all: [
       App\Models\Expense #4320
         expense_id: 1,
         user_id: 1,
         created_at: null,
         updated_at: null,
         user: App\Models\User #3382
           user_id: 1,
           employee_id: 1,
           created_at: null,
           updated_at: null,
           employee: App\Models\Employee #4335
             employee_id: 1,
             first_name: "john",
             last_name: "doe",
             created_at: null,
             updated_at: null,
           ,
         ,
       ,
       App\Models\Expense #4323
         expense_id: 2,
         user_id: 1,
         created_at: null,
         updated_at: null,
         user: App\Models\User #3382,
       ,
     ],
   
*/