How can I make a relation between tables in Laravel? - php

Question

I have three tables like these:
// users
+----+-----------+
| id | user_name |
+----+-----------+
| 1 | Jack |
| 2 | Peter |
| 3 | John |
+----+-----------+
// skills
+----+------------+
| id | skill_name |
+----+------------+
| 1 | PHP |
| 2 | HTML |
| 3 | Laravel |
| 4 | MySQL |
| 5 | jQuery |
+----+------------+
// skill_user
+----------+---------+
| skill_id | user_id |
+----------+---------+
| 2 | 1 |
| 5 | 1 |
| 1 | 2 |
| 2 | 2 |
| 4 | 2 |
+----------+---------+
Now I want to get all skills of one specific user. I can do that by using a join clause in a raw sql query:
SELECT s.skill_name
FROM skills s
JOIN skill_user su ON s.id = su.skill_id
WHERE su.user_id = :user_id
/* output (assuming :user_id is 1)
+------------+
| HTML |
| jQuery |
+------------+
Ok All fine. Now I want to know, how can I do that by adding a method in the model of Laravel framework? All I'm trying to do is using belongsTo(), hasOne(), hasMany() etc ..

Answer 1

To do in Eloquent way, you need to add the relationship. In your case, it is many-to-many relationship so in User.php, add this function to declare the relationship:
public function skills() {
$this->belongsToMany(\App\Skill::class, 'skill_user', 'user_id', 'skill_id');
}
Then,
Access it like this to eager load it:
$users = \App\User::with('skills')->get();
OR
Say you have a single user,
$user = User::where('id', 1)->first(); // Get the user with id = 1
and to get the skill for that user:
$user->skills;
OR
If you don't want to do using Eloquent way, you can use Query Builder. Note that, using this method, you basically join it manually so you don;t need to add any method to the Model:
\DB::table('users')
->join('skill_user', 'skill_user.user_id','=', 'users.id')
->join('skills', 'skill_user.skill_id', '=', 'skills.id')
->select('*')
->where('users.id', 1)
->get();

Answer 2

You have to use belongsToMany relationships. Assuming you will create SkillUser model for skill_user table. Add the following code to User Model
public function skills() {
$this->belongsToMany('App\SkillUser', 'skill_user', 'user_id', 'skill_id');
}
Now you can access it by
$users->skills();

Answer 3

I assume you are talking about Many to Many relationship between Users and skills, then the example given in Laravel many-to-many speaks about it.