[basex-talk] Can't update or delete JSON objects

I have tried XQUERY updates that should work but they don't work. My technique of storing JSON documents is perhaps not traditional. I have reduced my example to this simple example.

FRIST CREATE DATABASE WITH ONE DOCUMENT:

db:create('geography', json:parse('{ "code": "USA", "name": "United States of America", "birth": 1776 }'), '/country')

THEN ADD ANOTHER DOCUMENT:

db:add('geography', json:parse('{ "code": "CAN", "name": "Canada", "birth": 1867 }'), '/country')

1. How can I update either of these documents using 'code' as the unique identifier? 1. How can I change the 'name' or 'birth'? 2. How can I add a 'population' number? 2. How can I delete either of these documents using 'code' as the unique identifier?