Laravel relations with composite foreign keys

问题

Here's what I want to achieve, we have Staff and every staff can have one Position for a department, as well as one Designation for a department and multiple Additional Charges for multiple departments, one department per Additional Charge. And I want to store all the responsibilities in the staff_responsibilities table

I have a staff table with the following columns

id
name
email

Then I have staff_responsibilities table with the following columns:

staff_id
designation_id
department_id
responsibility_type_id

Responsibility types can be Position and Additional Charge and one staff can have multiple designations with Additional Charge responsibility.

Then I have a responsibility_types table with the following columns:

id
name


// I have no way to tell this relationship to look for a responsibility type 2 (2 is the id of the responsibility called `Designation`) 

public function designation()
    {
        return $this->hasOne(StaffResponsibility::class);
    }

// I have no way to tell this relationship to look for a responsibility type 2 
    public function position()
    {
        return $this->hasOne(StaffResponsibility::class);
    }

// Gives error: Syntax error or access violation: 1066 Not unique table/alias: 'staff_responsibilities' 
    public function additionalCharges()
    {
        return $this->belongsToMany(StaffResponsibility::class, 'staff_responsibilities','designation_id');
    }

Any help would really be appreciated.

staff_responsibilities table

responsibility_types table

designations table

回答1:

Here's what I want to achieve, we have Staff and every staff can have one Position for a department, as well as one Designation for a department and multiple Additional Charges for multiple departments, one department per Additional Charge.

It sounds to me like it would be beneficial to create a model for Position, Designation and Additional Charges. It feels like you may need to normalize your database or to change staff_responsibilities as a pivot table.

But hard to say without knowing your application.

To answer your question, you could add some scopes in StaffResponsibility

class StaffResponsibility extends Model{

    public function scopeDesignation($query)
    {
        return $query->where('responsibility_type_id','=',2);
    }

}

and use it

public function designation()
{
    return $this->hasOne(StaffResponsibility::class)->designation();
}

And the last one is a hasMany relation and not a manyToMany according to what you wrote:

public function additionalCharges()
{
    return $this->belongsTo(StaffResponsibility::class, 'staff_responsibilities','designation_id')->additionalCharges();
}

来源：https://stackoverflow.com/questions/61501540/laravel-relations-with-composite-foreign-keys

标签

laravel

eloquent

many-to-many

relationship