Laravel belongsToMany relation condition - php

Question

I have created many-to-many relation using belongsToMany function:
class Doctor extends Model
{
...
public function categories()
{
return $this->belongsToMany('App\Category', 'doctors_to_categories', 'doctor_id', 'category_id');
}
...
}
Now I want to create query with many-to-many condition. In SQL in would be:
SELECT *
FROM `doctors`
JOIN `doctors_to_categories`
ON `doctors_to_categories`.`doctor_id` = `doctors`.`id`
WHERE `doctors_to_categories`.`category_id` = 1
I have tried to achieve this like:
$doctors = Doctor::with(['categories' => function($query) {
$query->where('category_id', '=', 1);
}])->get();
Or
$doctors = Doctor::with(['categories' => function($query) {
$query->where('categories.id', '=', 1);
}])->get();
But it is not working. Any ideas how it should be? Thanks for any help.

Answer 1

The with() function does not actually introduce a join in your query, it just loads the relation of all models as a second query. So the with() function couldn't possibly change the original result set.
What you are looking for is whereHas(). This will add a WHERE EXISTS clause to the existing query.
$doctors = Doctor::with('categories')->whereHas('categories', function ($query) {
$query->where('categories.id', 1);
})->get();

Answer 2

Using ->with() doesn't actually limit the results of the Doctor::...->get() query; it simply tells Laravel what to return in the relationships attribute. If you actually want to enforce returning only Doctors that have a category 1 relationship, you need to use whereHas():
$doctors = Doctor::whereHas('categories', function($query) {
$query->where('categories.id', '=', 1);
// `id` or `categories.id` should work, but `categories.id` is less ambigious
})->get();

Answer 3

You can add whereHas condition for this. Try code below:
$doctors = Doctor::with('categories')->whereHas('categories', function($query) {
$query->where('id', 1);
})->get();