SQL - Copiar un valor en el nuevo registro insertado en una misma tabla

id      cantidad

12345      15

67890      17

insert into cantidad (id,ctd)values(12345,15);

insert into cantidad (ctd) select ctd from cantidad where id=12345;

MariaDB [Prueba]> desc cantidad;

+-------+---------+------+-----+---------+----------------+

| Field | Type    | Null | Key | Default | Extra          |

+-------+---------+------+-----+---------+----------------+

| id    | int(11) | NO   | PRI | NULL    | auto_increment |

| ctd   | int(11) | NO   |     | NULL    |                |

+-------+---------+------+-----+---------+----------------+

MariaDB [Prueba]> select * from cantidad;

+-------+-----+

| id    | ctd |

+-------+-----+

| 12345 |  15 |

| 12346 |  15 |

Insert into cantidad (id,(Select ctd from cantidad where I’d = 12345));