Question

Assuming that no new \(n\)-tuples are added, find a composite key with two fields containing the Airline field for the database in Table 8.

Short answer

Either flight number or departure time can be used in addition to Airline to form a valid composite key.

Step-by-step solution

Given data 

Table 8 is given.

Concept of sets

The concept of set is a very basic one. It is simple; yet, it suffices as the basis on which all abstract notions in mathematics can be built.\(A\)set is determined by its elements. If\(A\)is a set, write\(x \in A\)to say that\(x\)is an element of\(A\).

Simplify the expression

For flight number, we can see that there are no duplicate flight numbers within any Airline, so this could be a valid part of the composite key.

Nadir Airline has multiple flights which depart from gate 34, so gate number cannot be used. Nadir Airline also has multiple flights which go to Detroit, so it is also not valid.

No two flights for any given Airline have the same departure time, so in this instance it's a valid composite key, however, realistically, based on the intention of this relation, it would not be part of a good real world composite key.