# dict indexed to model names
    tables = {'str':'%s'}
    for x in ModelOne, ModelTwo:
        tables[x._meta.object_name] = x._meta.db_table

    cursor = connection.cursor()
    ex_str =  """\
    select field1, field2, sum(field3) from %(ModelOne)s where date between %(str)s and %(str)s 
    group by field1, field2
    """ % tables
    cursor.execute(ex_str, dates)
    sumt = cursor.fetchall()