Ajax form post to nodejs/orientdb .. Null values

Question

I'm trying insert form data to orientdb via nodejs. No problem if form full completed. But there should be optional fields in my project's form . (database properties "nullable")

How can i insert data when there are empty fields in form . Is there an easy way?

view ajax code :

$('#ykForm').on('submit', function(e) { 
    e.preventDefault(); 

     $.post("/url-adress",$(this).serialize(), function( data ) {
     $.each(data,function(i,obj)
                {....}

node app code :

 app.post('/url-adress', (req, res) => {

              db.query(
   'Insert into yukIlani (AdSoyad,Mobil,IlanID,saat,aadres,Aciklama,agirlik,ailce,AracTipi,asehir,b_ilce,b_Sehir,badres,baslik,eposta,Firma,firmaadres,hacim,KasaTipi,takipkodu,telefon) values (:ad, :mob, :id, :saat, :aadres, :aciklama, :agirlik, :ailce, :tasittipi, :asehir, :bilce, :bsehir, :badres, :baslik, :email, :fismi, :fadres, :hacim, :kasatipi, :kod, :ftel)',
 {
    params: {
      ad: req.body.adsoyad,
      mob: req.body.mobil,
      id: kod,
      saat: req.body.yuksaat,
      kod: kodcevirik,
      asehir: req.body.asehir,
      bsehir: req.body.bsehir,
      ailce: req.body.ailce,
      bilce: req.body.bilce,
      aadres: req.body.aadres,
      badres: req.body.badres,
      fismi: req.body.firmaismi,
      ftelefon: req.body.firmatelefonu,
      fadres: req.body.firmaadres,
      email: req.body.email,
      aciklama: req.body.aciklama,
      baslik: req.body.baslik,
      fadres: req.body.firmaadres,
      email: req.body.email,
      ftel: req.body.firmatelefonu,
      tasittipi: req.body.tasittipi,
      kasatipi: req.body.kasatipi,
      hacim: req.body.hacim,
      agirlik: req.body.agirlik
    }
  }
).then(function (response){
res.send(response);
});
});