Laravel join with 3 Tables - mysql

Question

I am building a Twitter-like app. There is a Feed in which I want to only show posts of Users who I follow.
I tried everything with joins, but nothing seems to work.
I have 3 tables: Users, Followers, Shares
The Tables look like this:
Users: id
Followers: user_id, follower_id
Shares: user_id
What I need to get is "ALL Shares WHERE share.user_id = followers.follower_id"
"ANDWHERE followers.user_id = users.id"
Assume, the users.id is 3, I tried this:
$shares = DB::table('shares')
->leftjoin('followers', 'shares.user_id', '=', 'followers.follower_id')
->leftjoin('users', 'followers.user_id', '=', 'users.id')
->where('users.id', 3)
->where('shares.user_id', 'followers.follower_id')
->get();
But it doesnt work.
Any help is appreciated :)

Answer 1

I believe your join is wrong:
$shares = DB::table('shares')
->join('users', 'users.id', '=', 'shares.user_id')
->join('followers', 'followers.user_id', '=', 'users.id')
->where('followers.follower_id', '=', 3)
->get();
I also suggest you to name your table as follows instead, it feels a bit more natural to say user has many followers through follows and user has many followees through follows.
Example
$shares = DB::table('shares')
->join('users', 'users.id', '=', 'shares.user_id')
->join('follows', 'follows.user_id', '=', 'users.id')
->where('follows.follower_id', '=', 3)
->get();
Model approach
I didn't realize you were using DB:: queries and not models. So I'm fixing the answer and providing a lot more clarity. I suggest you use models, it's a lot easier for those beginning with the framework and specially SQL.
Example of models:
class User extends Model {
public function shares() {
return $this->hasMany('Share');
}
public function followers() {
return $this->belongsToMany('User', 'follows', 'user_id', 'follower_id');
}
public function followees() {
return $this->belongsToMany('User', 'follows', 'follower_id', 'user_id');
}
}
class Share extends Model {
public function user() {
return $this->belongsTo('User');
}
}
Example of Model usage:
$my = User::find('my_id');
// Retrieves all shares by users that I follow
// eager loading the "owner" of the share
$shares = Share::with('user')
->join('follows', 'follows.user_id', '=', 'shares.user_id')
->where('follows.follower_id', '=', $my->id)
->get('shares.*'); // Notice the shares.* here
// prints the username of the person who shared something
foreach ($shares as $share) {
echo $share->user->username;
}
// Retrieves all users I'm following
$my->followees;
// Retrieves all users that follows me
$my->followers;

Answer 2

In terms of general MySQL syntax, this is best written:
SELECT * FROM USER a JOIN FOLLOWERS b ON (a.id = b.user_id) JOIN SHARES c on (b.follower_id = c.user_id) WHERE a.id = 3
will return a data set of all followers and their respective shares.
I believe you would want the following in Laravel
DB::table('USER')
->join('FOLLOWERS', 'USER.id', '=', 'FOLLOWERS.user_id')
->join('SHARES', 'FOLLOWERS.follower_id', '=', 'SHARES.user_id')
->where('USER.id', 3)
->get();

Answer 3

Instead of
->where('shares.user_id', 'followers.follower_id')
It should be
->whereRaw('shares.user_id=followers.follower_id')
because on the original example the 'followers.follower_id' is interpreted as a string.

Answer 4

$data[shares] = DB::table('shares')
->leftjoin('followers', 'shares.user_id', '=', 'followers.follower_id')
->leftjoin('users', 'users.id', '=', 'users.id')
->where('users.id','=', 3)
->get();
to see results.
print_r($data[shares]);die;
for other query Simply give discription of your table

Answer 5

First of all, go through users table and join it with followers table, and then with share table to get corresponding shares data of only followers. Here is the code
$shares = DB::table('users')
->leftjoin('followers', 'users.user_id', '=', 'followers.follower_id')
->leftjoin('shares', 'shares.user_id', '=', 'users.id')
->where('users.id', 3)
->get();