MySQL 8.0

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create table TableOne(id int, num varchar(5));
insert into TableOne(id, num) values
(1, 'abcde'),
(2, '01234'),
(3, '56789');
                                          
create table TableTwo(id int, num varchar(5));
insert into TableTwo(id, num)
select
  id,
  concat(
    coalesce(lag(right(num, 3)) over (order by id), 'xxx'), 
    coalesce(left(num, 2), '')
  ) num
from (
  select * from TableOne
  union all
  select max(id) + 1, null from TableOne
) t;
select * from TableTwo;


id
num


1
xxxab

2
cde01

3
23456

4
789