Data Modeling with ER Model Questions

• An ID-dependent entity is an entity whose identifier is a composite identifier where no portion of the composite identifier is an identifier of another entity.
• When designing a database, first identify the entities, then determine the attributes, and finally establish the relationships.
• A ternary relationship is so called because in contains two entities and one association between them.
• In a 1:N relationship, the parent is the entity on the one side of the relationship and the child is the entity on the N side of the relationship.
• An entity is something that can be identified in the user's work environment; something that the users want to track.
• An identifier typically uses more than one attribute.
• Relationship classes are associations between entity classes.
• Entity instances are associated by relationship classes.
• Composite identifiers consist of two or more attributes.
• All instances of an entity class have the same attributes.
• A maximum cardinality is the maximum number of entity instances that can participate in a relationship instance.
• Entities use identifiers while tables use keys.
• 1:1, 1:N and N:M relationships are also known as HAS-A relationships.
• An attribute describes the entity's characteristics.
• The degree of a relationship refers to the number of entity classes in the relationship.
• An identifier determines the type of relationship that an entity has.
• A recursive relationship is a relationship between an archetype and an instance of that archetype.
• A subtype entity is a special case of another entity called a supertype entity.
• An entity class is a collection of entities and is described by the structure of the entities in that class.
• A minimum cardinality is the minimum number of entity instances that may participate in a relationship instance.