Many thanks ! I shall indeed go Read The Fine Manual now.
In case I might have further questions I would like to come back, post my work and understanding, and ask for specific guidance on the aspects I can't fully solve myself.
Thanks again, Karsten
In the JSON column, one key can be seen present as other keys. But, when use json_object_keys, it did not turn up at all.
Is there a way to cast json column as text, and extract values from text?