Eloquent 计算嵌套关系

Question

| Data     | DataChildren   | Category
----------------------------------
|  id      | id             | id
|  name    | data_id        | name
|          | category_id    |
|          | name           |

数据模型：

public function data_children() {
   return $this->hasMany(DataChildren::class, 'data_id', 'id');
}

数据子模型：

public function category() {
     return $this->belongsTo(Category::class, 'category_id', 'id');
}

我想根据 Data id 通过 DataChildren 获取 Category 的计数。我只想从数据中获取类别记录，所以结果应该是这样的

name from category | Count of category for Data
-------------------------------------------------
Unpublished        |   1
Published          |   3

我试过使用这个但是 return null

Data::withCount(['category'=> function($query){return $query->groupBy('category_id');}])->find(1);

Answer 1

你需要使用many to many关系

在类别模型中：

 public function datas()
 {
        return $this->belongsToMany(Data::class, 'data_childerens', 'category_id', 'data_id');
 }

然后运行这个查询 withCount :

Category::withCount('datas')->get();

设置数据模型：

public function categories()
{
     return $this->belongsToMany(Category::class, 'data_childerens', 'data_id', 'data_id');
}

然后运行这个查询 withCount :

Data::with('categories')->withCount('datas')->get();

Eloquent 计算嵌套关系

Eloquent Count nested relationships

php

laravel

eloquent

eloquent-relationship

laravel-7