Despite the fact that there are a lot of other versions of databases that do not use relation data model, this one is the most used around the world. Relation databases use SQL, a structured query language, and provide ACID transaction properties. The goal of this diploma thesis is to present the relation database model and analyse two relation databases, DB2 and MySQL that are due to their security and flexibility among the most used in the world. The databases are presented from both theoretical and practical aspect. In the theoretical part, the term database, which is based on scientific literature and its features, history and properties are presented. The main goal is to present the advantages and disadvantages of relation databases. In addition to the description of the system, is a comparison between two popular databases, MySQL and DB2. In the practical portion, the performance of MySQL and DB2 is compared based on test scenarios on a HDD and SSD drives. The conclusion includes the findings and guides to choose the most suitable relation database for a specific problem.