Attributes An Attribute is a property of a given entity. For example, ROLL NO is a property of an entity STUDENT. An attribute instance is particular property of an individual entity instance.For example, Peter is the instance of STUDENT entity and the roll number 101 is the instance of attribute ROLL NO and also the [...]
Continue reading → For the system to be usable, it must retrieve data efficiently. The need for efficiency has led designers to use complex data structures to represent data in the database.Since many database-systems users are not computer trained, developers hide the complexity from users through several levels of abstraction, to simplify users’ interactions with the system: Physical [...]
Continue reading → Entities and Relationships Entities: Chen defined an entity as “a thing which can be easily identified”. An entity is any object, place, person, or activity about which data is recorded. Some examples of entity are STUDENT, COURSE and GRAD. In the diagramming technique, entities are named and represented inside a box. It is important [...]
Continue reading → There are various object based models. The most widely used is the Entity-Relationship [ER] model. It is accepted as the ideal data model for database design. Peter Chen introduced this model in 1976, and since then, several people have added value to it. The ER Model The ER model is based on a perception of [...]
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