Here is a working code for extracting values from one container, transform to JSON and upload it in an API endpoint. Variations can easily be added.
select htp.retrieval_duration_ms
, htp.Bytes_retrieved
, htp.retrieval_successful
, htp.http_status_code
from ( select *
from my_table@container
for json auto
, root
) rqe
join httpdownload@DataDictionary
( url => 'https://my-enpoint.com/'
, contentType => 'application/json'
--, headers => 'Authorization=Bearer my_bearer'
--, basicAuthenticationUser => 'to_login'
--, basicAuthenticationPassword => 'my_pwd'
--, add request_timeout if needed
, method => 'POST'
, textpayload => rqe.JSON
) htp