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Entity-relationship diagram (ERD)
Visual representation of entities in db and relationships
Functions
Acts as documentation for database designs
Facilitations communication between stakeholders
Support future development and maintenance of db
Ensure data integrity and consistency through constraints and well-defined relationships
I. Crow’s foot notation
Type of ERD including modality, cardinality
Modality (I)
Defines optionality of relationship (optional: 0; mandatory: 1)
Innermost symbol from entity
Minimum

Cardinality (I)
Max no. of times instance in one entity can be associated with instances in related entity
Describes type of relationship (one-to-one, etc)
Maximum
Outermost symbol

EXAMPLES
Ex of how to read modality, cardinality







