CREATE TABLE SYMPTOMS (
  ID D_ID,
  PARENT_ID D_ID_OR_NULL,
  ORD_NUM_EN D_NUM,
  ORD_NUM_RU D_NUM,
  -- Много всякого
  PRIMARY KEY (ID),
  FOREIGN KEY (PARENT_ID) REFERENCES SYMPTOMS (ID) ON DELETE CASCADE
);

def del_some_child(connection, parent_id, mast_del):
  curs = connection.Cursor()
  curs.execute('select ID, ORD_NUM_EN, ORD_NUM_RU from SYMPTOMS where PARENT_ID = ? order by ORD_NUM_EN', [parent_id])
  childs = [(cid, ne, nr) for cid, ne, nr in curs]
  for cid, n in childs:
    if mast_del(cid):
      curs.execute('delete from SYMPTOMS where ID = ?', [cid])
      curs.execute(
        'update SYMPTOMS set ORD_NUM_EN = ORD_NUM_EN - 1 where PARENT_ID = ? and ORD_NUM_EN > ?', [parent_id, ne])
      curs.execute(
        'update SYMPTOMS set ORD_NUM_RU = ORD_NUM_RU - 1 where PARENT_ID = ? and ORD_NUM_RU > ?', [parent_id, nr])
  connection.commit()

$ lsb_release -drc
Description:    Ubuntu 14.04.2 LTS
Release:        14.04
Codename:       trusty

execute block
as
declare id integer;
declare ne integer;
declare nr integer;
declare pid integer = 470108;
begin
  for select r.ID, r.ORD_NUM as ORD_NUM_EN, r.ORD_NUM_RU
    from SYMPTOMS r
    where r.PARENT_ID = :pid -- and r.ID < 471000
    order by r.ORD_NUM
  into :id, :ne, :nr do begin
    if (:id > 471000) then begin
      delete from SYMPTOMS where ID = :id;
      update SYMPTOMS set ORD_NUM = ORD_NUM - 1 where PARENT_ID = :pid and ORD_NUM > :ne;
      update SYMPTOMS set ORD_NUM_RU = ORD_NUM_RU - 1 where PARENT_ID = :pid and ORD_NUM_RU > :ne;
    end
  end
end

execute block
as
declare id integer;
declare ne integer;
declare nr integer;
declare pid integer = 470108;
begin
  for select r.ID from SYMPTOMS r where r.PARENT_ID = :pid order by r.ORD_NUM
  into :id do begin
    if (:id > 471000) then begin
      select r.ORD_NUM, r.ORD_NUM_RU
        from SYMPTOMS r where r.ID = :id
        into :ne, :nr;
      delete from SYMPTOMS where ID = :id;
      update SYMPTOMS set ORD_NUM = ORD_NUM - 1 where PARENT_ID = :pid and ORD_NUM > :ne;
      update SYMPTOMS set ORD_NUM_RU = ORD_NUM_RU - 1 where PARENT_ID = :pid and ORD_NUM_RU > :nr;
    end
  end
end