[Zope] How to insert NULL values

[Jose Soares]

Hi all,

I'm trying to insert NULL values into a column of a table
using the ZSQL-Method without success.

I tried the following:

      <dtml-call "qry.ins_introduzioni(
                  codice_fiscale=CODICE_FISCALE,
                  distretto=DISTRETTO,
                  marca_precedente=''
       >")

also:

      <dtml-call "qry.ins_introduzioni(
                  codice_fiscale=CODICE_FISCALE,
                  distretto=DISTRETTO,
                  marca_precedente=_.None
       >")

Please may somebody tell me the right syntax?

Thank you.

Jose'