UPDATE d_debtor_info set debtor_id_num=insert(debtor_id_num, 8, 4, '****') where id=2667;
UPDATE d_debtor_info set work_telephone=insert(work_telephone, 4, 4, '****') where id=2667;

insert(debtor_id_num, 8, 4, '****')  从第8位开始，替换4位数据为****