An RDMS is a database that stores data in tables using rows and columns. The values in the tables are related to one other, and the tables may also be related to one another, hence the term relational. This relationship makes it possible to access data across multiple tables with a single query.
In this section, we will review the top four relational database management systems. The top four are Oracle, MySQL, SQL Server, and PostgreSQL.
According to the DB-Engines Ranking, here are the scores for the top RDMSes at the time of writing this book:
The preceding screenshot can be found at https://db-engines.com/en/ranking.