DBMS Tutorials

  Relational Data Model:-Brief History, Terminology in Relational Data Structure, Relations, Properties of Relations, Keys, Domains, Integrity Constraints over Relations What is Relational Model? Relational Model  represents the database as a collection of relations. A relation is nothing but a table of values. Every row in the table represents a collection of related data values. These rows in the table denote a real-world entity or relationship. The table name and column names are helpful to interpret the meaning of values in each row. The data are represented as a set of relations. In the relational model, data are stored as tables. However, the physical storage of the data is independent of the way the data are logically organized. The History of the Relational Model The relational model for database introduced by a gentleman named E.F. Codd. Codd developed the model in a 1970 research paper. His concepts were put into practice in the late 70's in an IBM product called  System

  Basic Concepts of Hierarchical and Network Data Model Network data model In the network data model, data model data are represented by collections of records. Relationships among data are represented by links. In this data model, graph data structure is used. It permits a record to have more than one parent.                                             Figure - Network Data model This is an extension of the Hierarchical model. In this model data is organized more like a graph, and are allowed to have more than one parent node. In this database model data is more related as more relationships are established in this database model. Also, as the data is more related, hence accessing the data is also easier and fast. This database model was used to map many-to-many data relationships. Advantages of Network data model The Network data model is also conceptually simple and easy to design. In the network data model relationships like one-to-one and many-to-many are exist. In the network dat

Entity Relationship Diagram  An  Entity–relationship model (ER model)  describes the structure of a database with the help of a diagram, which is known as  Entity Relationship Diagram (ER Diagram) . An ER model is a design or blueprint of a database that can later be implemented as a database. The main components of E-R model are: entity set and relationship set. ER model stands for an Entity-Relationship model. It is a high-level data model. This model is used to define the data elements and relationship for a specified system. It develops a conceptual design for the database. It also develops a very simple and easy to design view of data. In ER modeling, the database structure is portrayed as a diagram called an entity-relationship diagram. What is an Entity Relationship Diagram (ER Diagram)? An ER diagram shows the relationship among entity sets. An entity set is a group of similar entities and these entities can have attributes. In terms of DBMS, an entity is a table or attribute o