Laravel 8 多表关系答案

【问题标题】：Laravel 8 Multiple Table RelationshipLaravel 8 多表关系
【发布时间】：2021-11-18 03:45:08
【问题描述】：

这是一个很长的帖子，提前抱歉。

我有几个关于下图的问题。

如何为这些表创建关系？（试过“belongsToMany”和“hasMany”）
我应该使用 Eloquent 还是 Query Builder 来获得想要的结果？（图片附在下面以获得所需的结果）
“client_order_items”是数据透视表吗？
如何区分数据透视表？是不是因为表有多个外键？
如何从“Manufacturer”模型访问“images”表？ “hasOneThrough / hasManyThrough”可以实现这一点吗？
仅使用 Eloquent 或 DB Query 是否可以达到预期的结果？

//sample:
Manufacturers::find(2)->client_order_items->cars->images->car_image

我尝试将“client_order_items”视为数据透视表，然后在“Manufacturer”、“Car”和“Car”中使用“belongsToMany”建立关系“ClientOrder”模型。

// App\Model\Manufacturer.php
public function client_orders() {
    return $this->belongsToMany(ClientOrder::class, 
           "client_order_items", "manufacturer_id", "client_order_id")
           ->withPivot('id', 'quantity', 'car_id');;
}
public function cars() {
    return $this->belongsToMany(Car::class, 
           "client_order_items", "manufacturer_id", "car_id");
}

// App\Model\Car.php
public function client_orders() {
    return $this->belongsToMany(ClientOrder::class, 
           "client_order_items", "car_id", "client_order_id");
}
public function manufacturers() {
    return $this->belongsToMany(Manufacturer::class, 
           "client_order_items", "car_id", "manufacturer_id");
}

// App\Model\ClientOrder.php
public function cars() {
    return $this->belongsToMany(Manufacturer::class, 
           "client_order_items", "client_order_id", "car_id");
}
public function manufacturers() {
    return $this->belongsToMany(Manufacturer::class, 
           "client_order_items", "client_order_id", "manufacturer_id");
}

我也尝试过“hasMany”关系：

// App\Model\Manufacturer.php
public function client_order_items() {
    return $this->hasMany(ClientOrderItems::class);
}

// App\Model\Cars.php
public function client_order_items() {
    return $this->hasMany(ClientOrderItems::class);
}

// App\Model\ClientOrder.php
public function client_order_items() {
    return $this->hasMany(ClientOrderItems::class);
}

// App\Model\ClientOrderItems.php
public function car() {
    return $this->belongsTo(Car::class);
}
public function manufacturer() {
    return $this->belongsTo(Manufacturer::class);
}
public function client_order() {
    return $this->belongsTo(ClientOrder::class);
}

如果我做了这样的事情，我的目标是得到结果：

// Manufacturer::find(2)->client_orders

// Desired Result:
[
    {
        "client_order_id": 88062,
        "first_name": "Clark",
        "last_name": "Kent",
        "order_items": [
            {
                "client_order_item_id": 37394,
                "quantity": 1,
                "car_id": 68,
                "image": "path_img1"
            }
        ]
    },
    {
        "client_order_id": 60978,
        "first_name": "Bruce",
        "last_name": "Wayne",
        "order_items": [
            {
                "client_order_item_id": 79913,
                "quantity": 1,
                "car_id": 68,
                "image": "path_img1"
            },
            {
                "client_order_item_id": 84743,
                "quantity": 1,
                "car_id": 95,
                "image": "path_img2"
            }
        ]
    }
]

但我目前得到的结果（使用“belongsToMany”）是：

// Manufacturer::find(2)->client_orders

// Current Result:
[
    {
        "id": 88062,
        "first_name": "Clark",
        "last_name": "Kent",
        "pivot": {
            "manufacturer_id": 2,
            "client_order_id": 88062,
            "id": 37394,
            "quantity": 1,
            "car_id": 68
        }
    },
    {
        "id": 60978,
        "first_name": "Bruce",
        "last_name": "Wayne",
        "pivot": {
            "manufacturer_id": 2,
            "client_order_id": 60978,
            "id": 79913,
            "quantity": 1,
            "car_id": 68
        }
    },
    {
        "id": 60978,
        "first_name": "Bruce",
        "last_name": "Wayne",
        "pivot": {
            "manufacturer_id": 2,
            "client_order_id": 60978,
            "id": 84743,
            "quantity": 1,
            "car_id": 95
        }
    }
]

再次为这篇长文感到抱歉。提前谢谢你。

【问题讨论】：

标签： php mysql eloquent laravel-8 laravel-query-builder

【解决方案1】：

经过几个小时的实验和阅读，我得到了我想要的结果。

建立关系：

Manufacturer 模型与“ClientOrder”具有“belongsToMany”关系

// App\Model\Manufacturer
public function client_orders() {
    return $this->belongsToMany(ClientOrder::class, 'client_order_items', 'manufacturer_id', 'client_order_id');
}

“Car”和“Image”模型具有“hasMany”关系。这将使我们能够从“ClientOrderItems”模型访问“Image”模型。

// App\Models\Car
public function image() {
    return $this->belongsTo(Image::class);
} 
 
// App\Models\Image
public function cars() {
    return $this->hasMany(Car::class);
}

为模型创建访问器

在“ClientOrder”模型中，为“order_items”键创建一个访问器。这将从“OrderLineItems”中获取与“manufacturer_id”和“client_order_id”相关的行。

// App\Models\ClientOrder
protected $appends = ["order_items"];

public function getOrderItemsAttribute() {
    $items = ClientOrderItems::where("manufacturer_id", '=', $this->pivot->manufacturer_id)
        ->where("client_order_id","=",$this->pivot->client_order_id)
        ->select(["id as client_order_item_id","car_id","quantity"])
        ->get();
    return $items;
}

在“ClientOrderItems”枢轴模型中，为“图像”创建一个访问器。

// App\Models\ClientOrderItems
protected $appends = ["image"];

public function getImageAttribute() {
    return Car::find($this->car_id)->image->car_image;
}

上面 2 个代码的结果如下所示：

[
    {
        "client_order_item_id": 79913,
        "quantity": 1,
        "car_id": 68,
        "image": "path_img1"
     },
     {
        "client_order_item_id": 84743,
        "quantity": 1,
        "car_id": 95,
        "image": "path_img2"
     }
]

有关访问器和突变器的更多信息： https://laravel.com/docs/8.x/eloquent-mutators#accessors-and-mutators

检索记录

要获取与manufacturer_id相关的“客户订单”，请使用：

/// App\Http\Controllers\ManufacturerController;
public function index() {
    $client_order = Manufacturer::find($manufacturer_id)->client_orders->unique("id")->values();
}

上面的代码只会从“client_orders”表中获取唯一的行。在访问器的帮助下为每一行附加相关的“order_items”。

[
    {
        "client_order_id": 88062,
        "first_name": "Clark",
        "last_name": "Kent",
        "order_items": [
            {
                "client_order_item_id": 37394,
                "quantity": 1,
                "car_id": 68,
                "image": "path_img1"
            }
        ]
    },
    {
        "client_order_id": 60978,
        "first_name": "Bruce",
        "last_name": "Wayne",
        "order_items": [
            {
                "client_order_item_id": 79913,
                "quantity": 1,
                "car_id": 68,
                "image": "path_img1"
            },
            {
                "client_order_item_id": 84743,
                "quantity": 1,
                "car_id": 95,
                "image": "path_img2"
            }
        ]
    }
]

【讨论】：