Returns an Orange datatype for a given mysql column.

            :param table_name: target table name
            :param col: column to determine the Orange datatype

def orng_type(self, table_name, col):
        '''
        Returns an Orange datatype for a given mysql column.

            :param table_name: target table name
            :param col: column to determine the Orange datatype
        '''
        mysql_type = self.types[table_name][col]
        n_vals = len(self.db.col_vals[table_name][col])
        if mysql_type in OrangeConverter.continuous_types or (
                        n_vals >= 50 and mysql_type in OrangeConverter.integer_types):
            return 'c'
        elif mysql_type in OrangeConverter.ordinal_types + OrangeConverter.integer_types:
            return 'd'
        else:
            return 'string'