There are several popular SQL database engines, such as PostgreSQL, MySQL (https://www.npmjs.com/package/mysql), and MariaDB (https://www.npmjs.com/package/mariasql). Corresponding to each are Node.js client modules similar in nature to the sqlite3 module that we just used. The programmer is close to the SQL, which can be good in the same way that driving a stick shift car is fun. But what if we want a higher-level view of the database so that we can think in terms of objects rather than rows of a database table? Object Relation Mapping (ORM) systems provide such a higher-level interface and even offer the ability to use the same data model with several databases.
The Sequelize module (http://www.sequelizejs.com/) is Promise-based, offers strong, well-developed ORM features, and can connect with SQLite3, MySQL, PostgreSQL, MariaDB, and MSSQL. Because Sequelize is Promise-based, it will fit naturally with the Promise-based application code we're writing...