SELECT host, json_to_string(j)
FROM t_json2_compat
ORDER BY host;

+--------+------------------------------------------+
| host   | json_to_string(t_json2_compat.j)         |
+--------+------------------------------------------+
| host_a | {"a":10,"flag":true,"nested":{"b":"x"}}  |
| host_b | {"a":20,"flag":false,"nested":{"b":"y"}} |
| host_c | {"a":30,"flag":true,"nested":{"b":"z"}}  |
+--------+------------------------------------------+

SELECT host, json_get_int(j, 'a') AS a
FROM t_json2_compat
WHERE json_get_int(j, 'a') >= 20
ORDER BY host;

+--------+----+
| host   | a  |
+--------+----+
| host_b | 20 |
| host_c | 30 |
+--------+----+

SELECT host, json_get_string(j, 'nested.b') AS nested_b
FROM t_json2_compat
WHERE json_get_bool(j, 'flag') = true
ORDER BY host;

+--------+----------+
| host   | nested_b |
+--------+----------+
| host_a | x        |
| host_c | z        |
+--------+----------+

SHOW CREATE TABLE t_json2_compat;

+----------------+-----------------------------------------------+
| Table          | Create Table                                  |
+----------------+-----------------------------------------------+
| t_json2_compat | CREATE TABLE IF NOT EXISTS "t_json2_compat" ( |
|                |   "ts" TIMESTAMP(3) NOT NULL,                 |
|                |   "host" STRING NULL,                         |
|                |   "j" JSON NULL,                              |
|                |   TIME INDEX ("ts"),                          |
|                |   PRIMARY KEY ("host")                        |
|                | )                                             |
|                |                                               |
|                | ENGINE=mito                                   |
|                |                                               |
+----------------+-----------------------------------------------+