SQLSTATE[42000]:语法错误或访问冲突:1066 不是唯一的表/关系别名

Why am I getting this error? What's going on?

包括完整模型

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class Message extends Eloquent
{
    use PublishedTrait;
    use SoftDeletingTrait;

    /**
     * The database table used by the model.
     *
     * @var string
     */
    protected $table = 'messages';

    /**
     * The attributes that can be set with Mass Assignment.
     *
     * @var array
     */
    protected $fillable = ['subject', 'user_id', 'body', 'status'];

    /**
     * The attributes that should be mutated to dates.
     *
     * @var array
     */
    protected $dates = ['created_at', 'updated_at', 'deleted_at'];

    /**
     * Validation rules.
     *
     * @var array
     */
    protected $rules = [
        'subject' => 'required|max:255',
        'body' => 'required',
    ];

    /**
     * User relationship
     *
     * @return IlluminateDatabaseEloquentRelationsBelongsTo
     */
    public function user()
    {
        return $this->belongsTo(Config::get('email.user_model'));
    }

    public function assets()
    {
        return $this->belongsToMany('NamespaceModulesAssetsModelsAsset', 'message_assets');
    }

    /**
     * Participants relationship
     *
     * @return IlluminateDatabaseEloquentRelationsHasMany
     */
    public function participants()
    {
        return $this->belongsToMany('NamespaceModulesEmailModelsParticipant', 'participants', 'message_id', 'user_id')->withTimestamps();
    }

    /**
     * Recipients of this message
     *
     * @return IlluminateDatabaseEloquentRelationsHasMany
     */
    public function recipients()
    {
        return $this->participants()->where('user_id', '!=', $this->user_id);
    }

    /**
     * Returns the latest message from a thread
     *
     * @return NamespaceModulesEmailModelsMessage
     */
    public function getLatestMessageAttribute()
    {
        return $this->messages()->latest()->first();
    }

    /**
     * Returns threads that the user is associated with
     * @param $query
     * @param $userId
     * @return mixed
     */
    public function scopeForUser($query, $userId)
    {
        return $query->join('participants', 'messages.id', '=', 'participants.message_id')
            ->where('participants.user_id', $userId)
            ->where('participants.deleted_at', null)
            ->select('messages.*');
    }

    /**
     * Returns threads that the user is associated with
     * @param $query
     * @param $userId
     * @return mixed
     */
    public function scopeForUserWithDeleted($query, $userId)
    {
        return $query->join('participants', 'messages.id', '=', 'participants.message_id')
            ->where('participants.user_id', $userId)
            ->select('messages.*');
    }

    /**
     * Returns messages that the user has sent
     * @param $query
     * @param $userId
     * @return mixed
     */
    public function scopeByUser($query, $userId)
    {
        return $query->where('user_id', $userId);
    }

    /**
     * Returns threads with new messages that the user is associated with
     * @param $query
     * @param $userId
     * @return mixed
     */
    public function scopeForUserWithNewMessages($query, $userId)
    {
        return $query->join('participants', 'messages.id', '=', 'participants.message_id')
            ->where('participants.user_id', $userId)
            ->whereNull('participants.deleted_at')
            ->where(function ($query) {
                $query->where('messages.updated_at', '>', $this->getConnection()->raw($this->getConnection()->getTablePrefix() . 'participants.last_read'))
                    ->orWhereNull('participants.last_read');
            })
            ->select('messages.*');
    }

}

参与者

class Participant extends Eloquent
{
    use SoftDeletingTrait;

    /**
     * The database table used by the model.
     *
     * @var string
     */
    protected $table = 'participants';

    /**
     * The attributes that can be set with Mass Assignment.
     *
     * @var array
     */
    protected $fillable = ['message_id', 'user_id', 'last_read'];

    /**
     * The attributes that should be mutated to dates.
     *
     * @var array
     */
    protected $dates = ['created_at', 'updated_at', 'deleted_at', 'last_read'];

    /**
     * Thread relationship
     *
     * @return IlluminateDatabaseEloquentRelationsBelongsTo
     */
    public function message()
    {
        return $this->hasMany('NamespaceModulesEmailModelsMessage');
    }

    /**
     * User relationship
     *
     * @return IlluminateDatabaseEloquentRelationsBelongsTo
     */
    public function user()
    {
        return $this->belongsTo(Config::get('email.user_model'));
    }
}

推荐答案

通过 Laracat 官方 Slack 回答:

public function participants()
{
    return $this->belongsToMany('NamespaceModulesEmailModelsParticipant', 'PIVOT', 'message_id', 'user_id')->withTimestamps();
}