mysql - 使用 Eloquent Laravel 定义表与链接表主键的关系

Question

您好，我正在尝试弄清楚如何以 Eloquent 方式定义这种关系: Image Of Schema

我使用 belongs to many 将制造商和设备类型链接在一起，例如:

return $this->belongsToMany('App\Models\EquipmentType','equipment_types_manufacturers', 
      'manufacturer_id', 'equipment_type_id');

但是在尝试定义关系时我找不到如何从 equipment_model FK etml_id -> equipment_types_manufacturers PK 定义链接

return $this->hasMany('App\Models\EquipmentType','equipment_types_manufacturers', 
      'equipment_types_manufacturers_id', 'equipment_type_id');

sql中哪个失败

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'manufacturers.equipment_types_manufacturers_id' in 'where clause' (SQL: select * from equipment_models where exists (select * from manufacturers where equipment_models.equipment_types_manufacturers_id = manufacturers.equipment_types_manufacturers_id and manufacturer_id = 1) and exists (select * from equipment_types where equipment_models.equipment_types_manufacturers_id = equipment_types.equipment_types_manufacturers_id and equipment_type_id = 1))

我觉得这可以通过为链接表创建模型来实现，但我不确定这是否正确？

Answer 1

您正在尝试通过另一个模型/表格获取模型。您需要使用 hasManyThrough()。在您的 Manufacturer 模型中，尝试

public function equipments() {
    return $this->hasManyThrough(
        'EquipmentModel', 'EquipmentTypesManufacturer',
        'manufacturer_id', 'etml_id', 'id'
    );
}

在这里阅读更多:https://laravel.com/docs/5.4/eloquent-relationships#has-many-through