draw an er diagram on attendance management system
ENHANCED ENTITY RELATIONSHIP OR EXTENDED ENTITY RELATIONSHIP
entity relation model for hospital database
yes
is called specialization and generalization.
Entity-Relationship diagrams are useful for modelling data and the relationships between the data. They can be used when the constraints between data are relatively simple. They do not allow specification of interactions between the data or model how the data changes (there are no processes in Entity-Relationship). Entity-Relationship diagrams are most often used to model databases.
Entity-relationship model advantages and disadvantages AdvantagesDisadvantagesConceptual simplicityVisual representationEffective communicationIntegration with the relational database modelLimited constraint representationLimited relationship representationNo representation of data manipulationLoss of information
mandatory and optional
AdvantagesConceptual simplicityVisual representationEffective communicationIntegration with the relational database model
In software engineering, an Entity - Relationship model(ER model for short) is an abstract and conceptual representation of data. Entity-relationship modeling is a database modeling method, used to produce a type of conceptual schema or semantic data model of a system, often a relational database, and its requirements in a top-down fashion. Diagrams created by this process are called entity-relationship diagrams or ER diagrams.learn more www.ngprakasam.hpage.com
Participation (or optionality) concerns the involvement of entities i a relationship. Participation is about exceptions to the rule. An entity's participation is optional if there is a least one instance of an entity which does not participate in the relationship. An entity participation is mandatory if all instances of an entity must participate in the relationship.
An entity relationship model is a visual representation of the relationships between entities in a database. For example, in a university database, you could have entities such as "Student," "Course," and "Instructor," with relationships like "Student enrolls in Course" and "Instructor teaches Course." These relationships are represented by lines connecting the entities in a diagram, showing how they are connected and interact with each other.
er daigram and dfd retaurent management?