MariaDB [test]> SELECT JSON_REPLACE('{"a":"b"}','$.*','c');

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

| JSON_REPLACE('{"a":"b"}','$.*','c') |

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

| NULL                                |

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

1 row in set, 1 warning (0.000 sec)

MariaDB [test]> SHOW WARNINGS;

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

| Level   | Code | Message                                                                    |

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

| Warning | 4044 | Wildcards in JSON path not allowed in argument 2 to function 'json_update' |

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

1 row in set (0.000 sec)