Define the concept of aggregation. Give two examples of where this concept is useful.

Q) Define the concept of aggregation. Give two examples of where this concept is useful.

Answer: Aggregation is an abstraction through which relationships are treated as higher-level entities. Thus the relationship between entities A and B is treated as if it were an entity C. Some examples of this are:

a. Employees work for projects. An employee working for a particular project uses various

E-R diagram for favourite sports team statistics

Q) Design an E-R diagramfor keeping track of the exploits of your favourite sports team. You should store the matches played, the scores in eachmatch, the players in each match and individual player statistics for each match. Summary statistics should be modeled as

E-R diagram for marks database

Consider a database used to record the marks that students get in different exams of different course offerings.

a) Construct an E-R diagram that models exams as entities, and uses a ternary relationship, for the above database.

Answer :

E-R diagram for a university

A university registrar’s office maintains data about the following entities:

(a) courses, including number, title, credits, syllabus, and prerequisites;

(b) course offerings, including course number, year, semester, section number, instructor(s), timings, and

Explain the distinctions among the terms primary key, candidate key, and superkey.

Answer: A superkey is a set of one or more attributes that, taken collectively, allows us to identify uniquely an entity in the entity set. A superkey may contain extraneous attributes. If K is a superkey, then so is any superset of K. A superkey for which no proper subset is also a superkey is called a candidate