Zend_Auth_Adapter_DbTable 提供的参数未能生成有效的 sql 语句

The section of code that is causing this problem is $result = $auth->authenticate($authAdapter);. Infact the whole controller code is found below:

class AuthenticationController extends Zend_Controller_Action
{
public function init()
{
    $uri = $this->_request->getPathInfo();

    $activenav = $this->view->navigation()->findByUri($uri);
    $activenav->active = true;
}

public function indexAction()
{
    // action body
}

public function loginAction()
{

    if(Zend_Auth::getInstance()->hasIdentity())
    {
        $this->_redirect('index/index');
    }

    $request = $this->getRequest();
    $form = new Application_Form_LoginForm();
    if($request->isPost())
    {
        if($form->isValid($this->_request->getPost()))
        {

            $authAdapter = $this->getAuthAdapter();

            $username = $form->getValue('username');
            $password = $form->getValue('password');

            $authAdapter->setIdentity($username)
                        ->setCredential($password);

            $auth = Zend_Auth::getInstance();

            try
            {
                $result = $auth->authenticate($authAdapter);
            }
            catch (Exception $e) 
            {
                echo 'Caught exception: ',  $e->getMessage(), "
";
            }

                if ($result->isValid()) 
                {
                    $identity = $authAdapter->getResultRowObject();
                    $authstorage = $auth->getStorage();
                    $authstorage->write($identity);

                   $this->_redirect('index/index');
                }
                else
                {
                    $this->view->errorMessage = "User name or password is wrong";
                }
            }
        }

    $this->view->form = $form;


}

public function logoutAction()
{
    Zend_Auth::getInstance()->clearIdentity();
    $this->_redirect('index/index');
}

private function getAuthAdapter()
{
    $authAdapter = new Zend_Auth_Adapter_DbTable(Zend_Db_Table::getDefaultAdapter());
    $authAdapter->setTableName('users')
                ->setIdentityColumn('username')
                ->setCredentialColumn('password')
                ->setCredentialTreatment('SHA1(CONCAT(?,salt))');

    return $authAdapter;
}
}

我已经坚持了几天了，这让我发疯了.顺便说一句，我如何回显正在生成的实际 sql?谢谢大家

$adapter = new Zend_Auth_Adapter_DbTable(
    $db,
    'user',
    'login',
    'password',
    'UNHEX(MD5(CONCAT(?, passwordSalt)))'
);