Database Management System Interview Questions and Answers For Freshers and Experience Part-10
Total specialization exists when every instance of a supertype must also be an instance of a subtype. Partial specialization exists when every instance of a supertype does not have to be an instance of a subtype.
92. Explain the difference between an ERD and EER.
An EER includes everything in an ERD and an EER allows for more complex relationships than an ERD. An EER allows for object-oriented data modeling and include supertypes and subtypes entities and inheritance.
93. Explain the difference between the disjoint and overlap rule.
The disjoint rule states an entity instance of a supertype can only be a member of one subtype. The overlap rule states an entity instance of a supertype can be a member of multiple subtypes.
94. List the three types of business rules and define each of them.
A derivation is a statement that is derived from other knowledge. A structured assertion is a statement that expresses some aspect of the static structure of an organization. An action assertion is a statement of a constraint on the actions of an organization.
95. Explain how a scenario is used for business rules.
A scenario is used to test business rules. It is a short script that describes how a business reacts to certain situations.
96. Explain some of the main goals of normalization.
Normalization should minimize data redundancy. It should also simplify referential integrity constraints. Normalization will also make it easier to insert, update, and delete data. And finally, it provides better design.
97. List some of the properties of a relation.
Relations in a database have a unique name and no multivalued attributes exist. Each row is unique and each attribute within a relation has a unique name. The sequence of both columns and rows is irrelevant.
98. Explain what needs to happen to convert a relation to third normal form
First you must verify that a relation is in both first normal form and second normal form. If the relation is not, you must convert into second normal form. After a relation is in second normal form, you must remove all transitive dependencies.
99. Describe how a supertype/subtype relationship is mapped into a relation.
A separate relation is created for each supertype and subtype. The attributes common for all of the subtypes are assigned to the supertype. Each subtype has the primary key from the supertype assigned to it. A subtype discriminator is added to the supertype.
100. Describe domain constraints.
Domain constraints include entity integrity and referential integrity. The domain is a set of values that may be assigned to an attribute. The entity integrity rule states that no part of a primary key cannot be null. Referential integrity states that each foreign key value must match a primary key value or be null.