  Databases are considered to be integral part of modern information systems.
Almost every web or mobile application uses some kind of database. Database
management systems are considered to be a crucial element from both business
and technological standpoint. This paper divides different types of database
management systems into two main categories (relational and non-relational) and
several sub categories. Ranking of various sub categories for the month of
July, 2021 are presented in the form of popularity score calculated and managed
by DB-Engines. Popularity trend for each category is also presented to look at
the change in popularity since 2013. Complete ranking and trend of top 20
systems has shown that relational models are still most popular systems with
Oracle and MySQL being two most popular systems. However, recent trends have
shown DBMSs like Time Series and Document Store getting more and more popular
with their wide use in IOT technology and BigData, respectively.
