Laravel加入3桌

Question

我正在构建一个类似Twitter的应用程序.有一个Feed,我只想显示我关注的用户的帖子.

我用连接尝试了一切,但似乎没有任何效果.

我有3个表:Users,Followers,Shares

表格如下所示:

用户:id

粉丝:user_id,follower_id

股票:user_id

我需要得到的是"ALL Shares WHERE share.user_id = followers.follower_id""ANDWHERE followers.user_id = users.id"

假设,users.id是3,我试过这个:

$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();

但它不起作用.

任何帮助表示赞赏:)

Answer 1

我相信你的加入错了:

$shares = DB::table('shares')
    ->join('users', 'users.id', '=', 'shares.user_id')
    ->join('followers', 'followers.user_id', '=', 'users.id')
    ->where('followers.follower_id', '=', 3)
    ->get();

我也建议您命名表作为follows代替,感觉更自然一点说user has many followers through follows和user has many followees through follows.

例

$shares = DB::table('shares')
    ->join('users', 'users.id', '=', 'shares.user_id')
    ->join('follows', 'follows.user_id', '=', 'users.id')
    ->where('follows.follower_id', '=', 3)
    ->get();

模型方法

我没有意识到你使用的是DB::查询,而不是模型.所以我正在修复答案并提供更多清晰度.我建议你使用模型,对于那些从框架开始,特别是SQL的人来说,它更容易.

模型示例:

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');
    }
}

模型用法示例:

$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;