Encounter some issue along the way

1.MySQL DATE_SUB & DATE_ADD

(DATE_ADD(NOW(), INTERVAL 30 MINUTES)
(DATE_SUB(NOW(), INTERVAL 30 MINUTES)
(NOW() - INTERVAL '30' MINUTE)
(NOW() - INTERVAL '30' MINUTE) or
(NOW() - INTERVAL '30 MINUTES') or
(NOW() - '30 MINUTES'::INTERVAL)

2.MySQL RADIANS
Need to cast to real

SELECT RADIANS(lat::real);

3.DISTINCT on json field (v9.4.5)

SELECT DISTINCT id, json_field FROM driver;

Throw could not identify an equality operator for type json error.
Converting the json field to jsonb solve the problem