MariaDB [test]> create table t1 (i int) partition by list (i) ( partition p1 default);

Query OK, 0 rows affected (0.62 sec)

MariaDB [test]> insert into t1 values (null);

Query OK, 1 row affected (0.08 sec)

MariaDB [test]> select * from t1 where i is null;

+------+

| i    |

+------+

| NULL |

+------+

1 row in set (0.00 sec)

MariaDB [test]> alter table t1 partition by list (i) ( partition p1 values in (1), partition p2 default);

Query OK, 1 row affected (1.38 sec)

Records: 1  Duplicates: 0  Warnings: 0

MariaDB [test]> select * from t1 where i is null;

Empty set (0.01 sec)

create table t1 (i int) partition by list (i) ( partition p1 default);

insert into t1 values (null);

select * from t1 where i is null;

alter table t1 partition by list (i) ( partition p1 values in (1), partition p2 default);

select * from t1 where i is null;