29-06-2012, 12:58 PM
Entity Relationship Diagrams
Entity Relationship Diagrams.ppt (Size: 65.5 KB / Downloads: 158)
Entity
“An entity is a business object that represents a group, or category of data.”1
Do we know a similar concept?
Attribute
“An attribute is a sub-group of information within an entity.”1
Do we know a similar concept?
Entity Relationship Models
Mandatory Relationships
Optional Relationships
Many-to-Many Relationships
One-to-Many Relationships
One-to-One Relationships
Recursive Relationships
Resolving Many-to-Many Relationships
Many-to-many relationships should be avoided. We can resolve a many-to-many relationship by dividing it into two one-to-many relationships.