如何从三个相关表中获取数据及其模型关系？

如何解决如何从三个相关表中获取数据及其模型关系？

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

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

费用模型：-

 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');
}

我打电话是这样查看的：-

<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，应该如何？请帮忙！谢谢！

解决方法

我认为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关系，其中一个单个模型是一个或多个子模型的父模型。

试试这个。

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");
    }
}

// Employee model.
class Employee extends Model
{
    use HasFactory;

    protected $primaryKey = 'employee_id';

    public function user()
    {
        return $this->belongsTo(User::class,"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,employee: App\Models\Employee {#4330
         employee_id: 1,first_name: "john",last_name: "doe",},}

*/

// 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: App\Models\User {#3382
           user_id: 1,employee: App\Models\Employee {#4335
             employee_id: 1,App\Models\Expense {#4323
         expense_id: 2,user: App\Models\User {#3382},],}
*/

我建议你以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，请使用单个名词：

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;

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>