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Entity-Relationship (ER) model. Popular high-level conceptual data model. ER diagrams. Diagrammatic notation associated with the ER model. STEPS IN DATABASE DESIGN. Requirements collection and analysis. DB designers interview prospective DB users to understand and document data requirements. Data requirements.
Entity-Relationship (ER) Model. One ER Diagrammatic Notation. Requirements Elicitation. Approaches to Conceptual Design. Database Design and Implementation Process. Description of data requirements that is... Comprehensive. Entity types, relationships, and constraints. Sanity check of data & functional requirements.
Many-One Relationships. Some binary relationships are many -one from one entity set to another. Each entity of the first set is connected to at most one entity of the second set. But an entity of the second set can be connected to zero, one, or many entities of the first set.
Entity relationship diagrams (ERD) are widely used in database design and systems analysis to represent systems or problem domains. The ERD was introduced by Chen (1976) in early 1976. Teorey, Yang, and Fry (1986) present an extended ER model for relational database design.
Entity-Relationship Approach. (ER Approach or ER Model) Tok Wang Ling National University of Singapore. Topics. Concepts/Constructs in ER Approach and diagram. Cardinality vs. Participation Constraint. Weak Entity Type, EX/ID Relationship Types, generalization and specialization. Some extensions: Aggregation, Multiple FDs Representation.
A weak entity can be identified uniquely only by considering the primary key of another (owner) entity. Owner entity set and weak entity set must participate in a one-to-many relationship set (1 owner, many weak entities). Weak entity set must have total participation in this identifying relationship set.
Classify each relationship type identified in step 2 according to its multiplicity, i.e. if it is a one-to-one, many-to-one or many-to-many. Determine the participation constraints for each entity type in each relationship type. Draw an ERD with the entity types and the relationship types between them.
