I'm starting server-side development with NodeJS, I have found lots of promising frameworks, but can't tell which of them support relational databases (Namely Postgres).
Any ideas? Server-side MVC frameworks are preferred.
Express is universal framework ( and really popular one ), you can use it with any database you want. You just need a database driver. You can use one of these:
https://github.com/brianc/node-postgres ( low level )
https://github.com/grncdr/node-any-db
https://github.com/brianc/node-sql
There are probably many many more, just google it.
check out the modules list here
there are many db modules for mysql/SQLite/PostgreSQL etc...
I'd go with Sequelize.js. It's an ORM for Postgres and MySQL. It's recommended in some books about node.js. I gave it a try and it looked promising.
On the other hand I would ask myself a question: If I need to use relational database, is node.js still a good choice?
sails.js is built on express (see @freakish's answer) and supports MySQL, Postgres, and over a dozen other NoSQL and SQL databases.