Generate a base record if there are any base columns,
or if there is only one primary key coulmn (in which case
we will not generate a primary key class), or if there is only one
BLOB column (in which case we will not generate a record with
BLOBs class).
This method should return an XmlElement for the update by primary key
statement that updates all fields in the table - but only if the field is
not null in the parameter object.