Laravel Eloquent 3 查询合二为一答案

【问题标题】：Laravel Eloquent 3 queries into oneLaravel Eloquent 3 查询合二为一
【发布时间】：2018-06-27 05:43:29
【问题描述】：

我想要实现的是一次执行 3 个查询，以限制 n1+ 问题：

假设我们有 3 个模型：

trips
  id => int
  price => float
  city_id => uint
........

cities
  id => int
  name => varchar
........

ratings:
  id => int
  ratable_id => int
  rate => small-int
......

伪代码：

select from tours where price >= 100
-then from the result 
select from cities where id in result.city_id as cities
select count from ratings where ratable_id in result.id as rates groupBy rate

所以结果是

[
  trips => list of the trips where price more than or equal 100
  cities=> list of the cities those trips belongs to
  rates => list of rating with it's count so like [1 => 5, 2 => 100] assuming that '1 and 2' are the actual rating , and '5,100' is the trips count 
]

我将如何做到这一点？

【问题讨论】：

标签： php mysql laravel group-by laravel-5.6

【解决方案1】：

两种方法，使用 eloquent 方法（首选方法）或使用连接单个查询来获得所需的结果

以雄辩的方式前进，我假设您已经根据它们的关系类型（1：m，m：m）定义了模型及其映射

$trips= Trips::with('city')
            ->withCount('ratings')
            ->where('price', '>=', 100)
            ->get();

与加入一起前进

$trips = DB::table('trips as t')
            ->select('t.id', 't.price','c.name',DB::raw('count(*) as rating_count'))
            ->join('cities as c' ,'t.city_id', '=' , 'c.id')
            ->join('ratings as r' ,'t.ratable_id', '=' , 'r.id')
            ->where('t.price', '>=', 100)
            ->groupBy('t.id', 't.price','c.name')
            ->get();

【讨论】：

【解决方案2】：

出行模型关系

public function city(){
   return $this->belongsTo(City::class);
}

public function ratings(){
   return $this->hasMany(Rating::class, 'ratable_id'); //assuming ratable_id is an id of trips table
}

获取数据

$trips= Trip::with('city', 'ratings')
            ->where('price', '>=', 100)
            ->get();

打印数据

foreach($trips as $trip){
    $trip->city->name." - ". $trip->price." - ". $trip->ratings()->avg('rate');
}

【讨论】：