Hi @Sina36 and welcome to the KNIME community.
For the first part of your question, please see the following thread
For the second part, there is no one way to read from the database, and it Helens what you are trying to do so I would suggest taking a look at the db extensions guide
https://docs.knime.com/2019-06/db_extension_guide/index.html#intro
But as a quick start overview, there are some useful videos available:
