Date Added: Sep 2012
In this paper, the authors present a detailed study of the work to modeling the hierarchies and data trees in relational database area. Hierarchical structures are used in diverse domains, in engineering and in research. The hierarchical model database is the first to appear, the main problem of this system is the lack of independence of the programs with respect to data storage. However, the relational model remains more used. The Relational DataBases (RDB) provides an excellent support for the representation and storage of the data within information systems. This model is based to relational Algebra.