Connecting to databases is an essential part of building applications in Node.js. Node.js makes it easy to interface with a variety of databases including relational databases like MySQL, PostgreSQL, and SQLite, as well as NoSQL databases like MongoDB, Cassandra and Redis.

To connect to a database in Node.js, you first need to install a Node.js driver for that particular database. This driver allows Node.js to communicate with the database, send queries, and retrieve data. Once you have installed the driver, you can use the driver’s API to establish a connection to the database.

Once you have established a connection to the database, you can interact with the data by executing queries. To do that, you need to build SQL statements that are sent to the database. You can use query builders like Knex.js or ORMs like Sequelize or TypeORM to help you build these queries.

After running queries, you can also retrieve the data and manipulate it as necessary. Node.js offers support for handling data in different formats, including traditional JSON and binary formats. The data returned from the database can also be transformed into a specific data format so that it can be consumed by the application.

In conclusion, connecting to databases in Node.js is an important step toward building robust web applications. With the diverse array of databases that Node.js supports, using Node.js enables developers to work with the right database for their particular use case, which allows them to create more flexible, scalable, and efficient applications.