Day Of

Question 1

Completeness =

Answer 1

MUST an instance of supertype also be a member of at least one subtype.

Question 2

Total specialization rule:

Answer 2

Each instance of supertype MUST BE an instance of a subtype. Exhaustive. Double line towards circle.

Question 3

Partial Specialisation rule:

Answer 3

Entity instance of supertype is allowed NOT to belong to any subtype. Non-exhaustive. Single line towards circle.

Question 4

What are the two completeness constraint rules:

Answer 4

Total Specialisation and partial Specialisation (there may be other subtypes not yet defined).

Question 5

What is Disjointness constraint:

Answer 5

Can an instance of supertype be a member of two or more subtypes?

Question 6

What are the two rules for the Disjointness constraint in an erd?

Answer 6

The disjoint rule and the overlap rule.

Question 7

What is the disjoint rule:

Answer 7

An instance f the supertype can only be ONE subtype.’d’ -OR

Question 8

What is the overlap rule:

Answer 8

An instance of supertype can be more than one of the subtypes. ‘O’ - AND

Question 9

Subtype discriminator?

Answer 9

An attribute of supertype for determining which subtype it is: simple or Boolean.

Question 10

What is logical database design?

Answer 10

Transforming conceptual models (er and eer diagrams) into relations (relational schema).

Question 11

Two types of ERD constraints:

Answer 11

Completeness, Disjointness.