[Zope] NULL in datefields in DB and Zope

<color><param>0100,0100,0100</param>Hello, if there are no values in a column with dates in my database (mySQL) the database returns "0000-00-00". ZOPE says: "<bold><FontFamily><param>Times New Roman</param><bigger>Error Type: ValueError</bold> <bold>Error Value: Invalid value, 0000-00-00, for Faelligkeit in record 2</bold> <FontFamily><param>Arial</param><smaller>The exception is raised in:<FontFamily><param>Times New Roman</param><bigger> ...\lib\python\Shared\DC\ZRDB\RDB.py, line 272 <FontFamily><param>Arial</param><smaller>How can I get the records with NULL-values in datefields with a ZSQL-Method? Regards, Egon<FontFamily><param>Times New Roman</param><bigger> <FontFamily><param>Arial</param><smaller> <nofill>