WHAT ARE HIERARCHICAL, NETWORK, AND RELATIONAL DATABASE MODELS?
Ans: a) Hierarchical Model: The Hierarchical Model was introduced in the Information Management System (IMS) developed by IBM in 1968. In this data is organized as a tree structure. Each tree is made of nodes and branches. The nodes of the tree represent the record types and it is a collection of data attributes entity at that point. The topmost node in the structure is called the root. Nodes succeeding lower levels are called children. b) Network Model: The Network Model, also called as the CODSYL database structure, is an improvement over the Hierarchical mode, in this model concept of parent and child is expanded to have multiple parent-child relationships, i.e. any child can be subordinate to many different parents (or nodes). Data is represented by collection of records, and relationships among data are represented by links. A link is an association between precisely two records. Many-to-many relationships can exists between the parent and child. c) Relational Model: The Relationa
