Ben bu linkte ki kütüphaneyi kullanıyorum.
**pod 'SQLClient', :git => 'https://github.com/martinrybak/SQLClient.git’**
Yukarıdaki gibi önce projene import et bu kütüphaneyi Xcode kapalı olsun.
Daha sonra Xcode aç projeni  build/clean ettikten sonra 
aşağıda bir örnek kod paylaşıyorum bir deneyebilirsin.
import Foundation
import UIKit
class deneme: UIViewController, SQLClientDelegate {
    /**
     *  Required delegate method to receive error notifications
     *
     *  @param error    Error text
     *  @param code     FreeTDS error code
     *  @param severity FreeTDS error severity
     */
    func error(_ error: String!, code: Int32, severity: Int32) {
        print(error)
        if(!error.isEmpty){
            let refreshAlert = UIAlertController(title: "", message: "", preferredStyle: UIAlertControllerStyle.alert)
            refreshAlert.addAction(UIAlertAction(title: "", style: .default, handler: { (action: UIAlertAction!) in
                //do something
            }))
            present(refreshAlert, animated: true, completion: nil)
        }
    }
    let client = SQLClient.sharedInstance()
    override func viewDidLoad() {
        denemeFunc { (isResponse) in
            // true ise buraya girer
        }
    }
    func denemeFunc(_ completionHandler : @escaping ((_ isResponse : Bool) -> Void)) {
        client?.delegate = self
        client?.connect(macAddress+":"+portNoSon, username: username, password: password, database: databaseName) {
            success in
            if success {
                self.client?.execute("SQL SORGUSU BURADA" ) {
                    results in
                    for table in results as! [[[String:AnyObject]]] {
                        for row in table {
                            for (columnName,   value) in row {
                                print("\(columnName) = \(value)")
                                }
                            }
                        }
                    }
                    completionHandler(true)
                    self.client?.disconnect()
                }else{
                completionHandler(false)
            }
        }
    }
}