The goal of this article is to introduce the basic characteristics of the databases modelling tools and to show how they are used through our own practical example. The main concepts regarding the article are defined in the introduction and the problem that will be described is presented. The criteria for the comparison of the given tools has been defined using previous research. The relational model of our “Fitness studio” business case has been the basis for the comparison of three database modelling tools: ER/Studio, ModelRight and SQL Power Architect. The tools were described and compared with regards to the chosen criteria.