laravel belongstomany with condition - php

Question

I have the following model.
class Training extends \Eloquent {
// Add your validation rules here
public static $rules = [
'name' => 'required',
'city' => 'required',
'province' => 'required',
'budget_year' => 'required|integer',
's_date' => 'required|date',
'e_date' => 'required|date'
];
// Don't forget to fill this array
protected $fillable = [
'name',
'city',
'province',
'budget_year',
's_date',
'e_date'
];
public function material(){
return $this->hasMany('Material');
}
public function budget(){
return $this->belongsToMany('Budget')->withPivot('amount');
}
public function budgetById($training_id){
$this->belongsToMany('Budget')->where('training_id', '=', $training_id)->get();
}
}
when I debug the budgetById method using DB::getQueryLog, the query is as follow
select budgets.*,
budget_training.training_id as pivot_training_id,
budget_training.budget_id as pivot_budget_id
from budgets inner join budget_training on budgets.id = budget_training.budget_id
where budget_training.training_id is null and training_id='6'
which return 0 rows, but when I try to modify the query and run it in pgadmin, the following script works well.
select budgets.*,
budget_training.training_id as pivot_training_id,
budget_training.budget_id as pivot_budget_id
from budgets inner join budget_training on budgets.id = budget_training.budget_id
where budget_training.training_id='6'
notice I remove training_id is null and from Laravel generated query. What is wrong with my budgetById method?

Answer 1

You have called get() and didn't use return here:
public function budgetById($training_id){
// = in where is optional in this case
$this->belongsToMany('Budget')->where('training_id', '=', $training_id);
}
You should use like this:
public function budgetById($training_id){
// = in where is optional in this case
return $this->belongsToMany('Budget')->where('training_id', '=', $training_id);
}

Answer 2

In Lavarel 7.X, you can use the wherePivot method to filter columns on the pivot table, like this:
return $this->belongsToMany('Budget')->wherePivot('training_id', '=', $training_id);
or
return $this->belongsToMany('Budget')->wherePivotNotNull('training_id');