- A public data-base where data can't be altered (immutability)
- Some records which store history like medical records which can only be updated by not overwritten.
On the technical end, it's decentralised and hence there is no central authority over the database.
So, this database allows only INSERT and SELECT WHERE id=? and UPDATE ... WHERE id=? or it also allows more complex queries?
most SQL-92 standard is supported. that is you can even write SQL like this:
FROM urls
LEFT JOIN
(SELECT *
FROM (SELECT url_id AS uid, max(retrieval_time) AS rtime
FROM lookups GROUP BY 1 ORDER BY 1)
WHERE uid IN (358341,358341,358341)
) recent
ON u.source_seed_id = recent.xyz OR u.url_id = recent.xyz
WHERE
DATETIME(recent.rtime) > DATETIME('now', '-5 days');