BTW, Oracle supports this under the name "continuous query notification".

https://docs.oracle.com/en/database/oracle/oracle-database/2...

You can get callbacks from the driver as query results change, or have notifications be sent to stored procedures, or posted to a message queue (and from there turned into web hooks etc). The notification comes with info about the deltas.

The main issue with it is that the queries it can monitor live are a subset of all queries. It's really more like using SQL to select database cells to watch, than propagating changes through arbitrary query plans. For example, it can't handle a SELECT COUNT(*) FROM statement. Obviously you can use it as a trigger for re-running more advanced queries though.