MySQL 5.7

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create table cityX (
  id int primary key not null auto_increment,
  code char(5),
  place int );
insert into cityX (code, place) values
('001x',1),('001x',2),('002x',1),('003x',2);
select * from cityX
order by code, place;


id
code
place


1
001x
1

2
001x
2

3
002x
1

4
003x
2


insert into cityX (code, place)
select x.code,1 from cityX x
where place = 2
and not exists
(select id from cityX c
where c.code = x.code
and place = 1);
insert into cityX (code, place)
select x.code,2 from cityX x
where place = 1
and not exists
(select id from cityX c
where c.code = x.code
and place = 2);
select * from cityX
order by code, place;


id
code
place


1
001x
1

2
001x
2

3
002x
1

6
002x
2

5
003x
1

4
003x
2