Support for Oracle Database Continuous Query Notifications, allowing JavaScript methods to be called when database changes are committed. This is a cool feature useful when applications want to be notified that some data in the database has been changed by anyone.

I recently posted a demo showing CQN and Socket.IO keeping a notification area of a web page updated. Check it out.

The new node-oracledb connection.subscribe() method is used to register a Node.js callback method, and the SQL query that you want to monitor. It has two main modes: for object-level changes, and for query-level changes. These allow you to get notifications whenever an object changes, or when the result set from the registered query would be changed, respectively. There are also a bunch of configuration options for the quality-of-service and other behaviors.

It's worth noting that CQN requires the database to establish a connection back to your node-oracledb machine. Commonly this means that your node-oracledb machine needs a fixed IP address, but it all depends on your network setup.

Oracle Database CQN was designed for infrequently modified tables, so make sure you test your system scalability.