MariaDB [test]> select json_object('a', json_object('b', 'c'));

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

| json_object('a', json_object('b', 'c')) |

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

| {"a": {"b": "c"}}                       |

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

1 row in set (0.000 sec)

MariaDB [test]> select json_object('a', if(1, json_object('b', 'c'), json_object('e', 'f')));

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

| json_object('a', if(1, json_object('b', 'c'), json_object('e', 'f'))) |

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

| {"a": "{\"b\": \"c\"}"}                                               |

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

1 row in set (0.001 sec)

MariaDB [test]> select json_object('a', coalesce(json_object('b', 'c')));

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

| json_object('a', coalesce(json_object('b', 'c'))) |

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

| {"a": "{\"b\": \"c\"}"}                           |

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

1 row in set (0.000 sec)