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Laravel - Additional relationship on a pivot table

Question:

I have a regular pivot table with 2 keys. However, I also have a 3rd column where I want to store a different key with a one to many relationship. Is this possible to have?

Example:

Pivot table:<br /> Organization 1 | Organization 2 | Relation type<br /> 1 | 2 | 1<br /> 1 | 3 | 2

In this case organization number 1 has a relation with organization number 2 with the relation type being number 1. Organization number 1 also has a relation with organization number 3 with relation type 2.

Now is my question, how do I set up that additional one to many relationship on the pivot table?

Answer1:

What you have here is a ternary relationship. You are saying that an organisation A relates with an organisation B and a relationship type. This is a very uncommon use case because in the vast majority of cases ternary relationships can be simplified to binary ones. You need a very deep inspection of your data model to determine whether your case can be simplified, but assuming that it can't here's my suggestions.

It's worth checking <a href="https://laravel.com/docs/5.5/eloquent-relationships#many-to-many" rel="nofollow">the eloquent docs</a> in particular under <em>Defining Custom Intermediate Table Models</em> for this. Note that this requires Laravel 5.4+ to work.

The following should work:

class OrganisationOrganisationLink extends Pivot { public relationType() { return $this->belongsTo(RelationType::class); //You need to specify the foreign key correctly as a 2nd parameter } }

Then in your original model:

class Organisation extends Model { public relatedOrganisation() { return $this->belongsToMany(self::class)->using(OrganisationOrganisationLink::class); } }

Then when making practical use of this you can e.g. do:

$organisation = Organisation::with('relatedOrganisation')->first(); echo "Got ".$organisation->name." which relates to " .$organisation->relatedOrganisation->first()->name ." with relationship type " $organisation->relatedOrganisation->first()->pivot->relationshipType()->value('name');

Of course the fields I've assumed may not exist but hopefully you get the idea.

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