Hierarchical Data in RDBMS

Relational databases are not well suited for representing and processing hierarchical data. Clever schemes are required to represent trees in the flat format of the relational model, as well as answering queries such as retrieving all nodes in a sub-tree, all nodes at a particular level and the nodes on the path from a node to one of its descendants. Some areas where hierarchical data needs to be stored and processed include XML data warehousing, organization chart in automation systems, bioinformatics and pyramidal games that require hierarchical data representation. In this book, a new method (Arya) is proposed to represent hierarchical data structures in relational database systems so that queries proved on trees can be executed efficiently. This method reshapes hierarchical data structures to non-hierarchical graphs using extra pointers to be accessed directly from each node to its ancestors. The cost for the gained performance is only a small increase in the space required for the representation of the original tree, which is significantly less than the used space by other methods.