Question

This is symbolized by a circle over a single line in an entity relationship diagram. It signifies that the supertype does NOT have to be one of the specified subtypes.

Partial completeness

Total completeness

System completeness

Associative completeness A supertype entity can contain as many as ____ subtype entities. 10 1 100 no defined limit When you set up an Entity Relationship Diagram, and have a many-to-many relationship, this entity is created to avoid problems inherent to a many-to-many relationship. Relational entity Composite entity Index entity Foreign entity You would this as a primary key when you don't have an attribute that makes sense or is a good choice for a primary key. Surrogate Automatic Candidate Composite Also known as bridge entities, these entities are used to implement M:N relationships and are composed of primary keys of each of the entities to be connected. Distinct Relationship Associative Primary You are designing an ERD for a local hospital to redo their database. You have identified a number of entities that you think could be subtypes. From these subtypes you need to create a supertype that will connect these subtypes. What is this type of process called? Disassociation Association Generalization Specialization

Answer 1

ANSWERS

1)Partial completeness

It means that not every supertype occurrence is a member of a subtype ,that is ,there maybe some supertype occurrences that are not members of any subtypes. It is symbolised by a circle over a single line.

2) No defined limit

Supertype is a generic entity type that has a relationship with one or more subtypes. A supertype entity can contain more than one subtype entities.

A subtype is a subgrouping of entities in an entity type whch share common attributes or relationships distinct from other subgroups.

3) Composite entity

Also known as Bridge entity, that helps to avoid problems inherent to many to many relationships. This entity lies between the two entities that are of interest and it shares the primary key from both the connecting tables.

4) Surrogate key

It is an artificial key which is used to uniquely identify each record. This kind of keys are unique because they are created when you don't have any natural primary key. They do not lend any meaning to the data in the table.

5) Associative entity

It is used to implement M:N relationship between two or more entities. This associative entity also called composite or Bridge entity is composed of primary keys of each of the entities to be connected.

6) Generalization

It is the process of extracting common properties from a set of entities (subtypes) and create a generalized high-level entity (supertypes) from it it. It is a bottom-up approach in which two or more entities can be generalized to a higher level entity if they have some attributes in common.

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