需要将OUTER JOIN转换为多个＆＃34; AND＆＃34;

Question

我有这个原始的sql我想转换为Esqueleto。它应该通过group表格将所有用户ID为1 group_membership的用户身份注册到SELECT * FROM group LEFT OUTER JOIN group_membership ON (group.id = group_membership.group_id AND group_membership.user_id=1) WHERE group_membership.group_id IS NULL 。

// First view controller

@IBAction func unwindActivitiesVCCellTapped( segue: UIStoryboardSegue )
{
    // table view cell tapped

    guard let activitiesVC = segue.sourceViewController as? ActivitiesVC else { return }

    print(activitiesVC.activityPerforming) // Displays nil in console output

    if let activityPerforming = activitiesVC.activityPerforming // thus this does not get called
    {
        activityPerformingButton.titleLabel?.text = activityPerforming
    }
}

// Second View Controller

class ActivitiesVC: UIViewController 
{
    @IBOutlet weak var activitiesTableView: UITableView!

    let activityTitles = [ "Walk" , "Run ", "Cycle", "Mountain Bike" ]

    var activityPerforming: String?

    override func viewDidLoad()
    {
        super.viewDidLoad()

        activitiesTableView.dataSource = self
        activitiesTableView.delegate   = self
    }
}

extension ActivitiesVC: UITableViewDelegate
{
    func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath)
    {
        activityPerforming = activityTitles[ indexPath.row ]
        print(activityPerfoming) // displays optional value I want
    }
}

// Custom Cell

class ActivityCell: UITableViewCell
{

    @IBOutlet weak var imageLabel    : UILabel!
    @IBOutlet weak var activityLabel : UILabel!

    override func awakeFromNib()
    {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(selected: Bool, animated: Bool)
    {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }
}