Laravel where on relationship object

问题

I'm developing a web API with Laravel 5.0 but I'm not sure about a specific query I'm trying to build.

My classes are as follows:

class Event extends Model {

    protected $table = 'events';
    public $timestamps = false;

    public function participants()
    {
        return $this->hasMany('App\Participant', 'IDEvent', 'ID');
    }

    public function owner()
    {
        return $this->hasOne('App\User', 'ID', 'IDOwner');
    }
}

and

class Participant extends Model {

    protected $table = 'participants';
    public $timestamps = false;

    public function user()
    {
        return $this->belongTo('App\User', 'IDUser', 'ID');
    }

    public function event()
    {
        return $this->belongTo('App\Event', 'IDEvent', 'ID');
    }
}

Now, I want to get all the events with a specific participant. I tried with:

Event::with('participants')->where('IDUser', 1)->get();

but the where condition is applied on the Event and not on its Participants. The following gives me an exception:

Participant::where('IDUser', 1)->event()->get();

I know that I can write this:

$list = Participant::where('IDUser', 1)->get();
for($item in $list) {
   $event = $item->event;
   // ... other code ...
}

but it doesn't seem very efficient to send so many queries to the server.

What is the best way to perform a where through a model relationship using Laravel 5 and Eloquent?

回答1:

The correct syntax to do this on your relations is:

Event::whereHas('participants', function ($query) {
    $query->where('IDUser', '=', 1);
})->get();

Read more at https://laravel.com/docs/5.8/eloquent-relationships#eager-loading

回答2:

@Cermbo's answer is not related to this question. in this answer, Laravel will give you all Events if per Event has 'participants' with IdUser is 1.

But if you want to get all Events with all 'participants' provided that per 'partecipants' with IdUser is 1, then you should do something like this :

Event::with(["participants" => function($q){
    $q->where('participants.IdUser', '=', 1);
}])

attention to:

in where use your table name, no Model name.

来源：https://stackoverflow.com/questions/29989908/laravel-where-on-relationship-object