Database Management System
Q83.
Consider the following statements S1 and S2 about the relational data model: S1: A relation scheme can have at most one foreign key. S2: A foreign key in a relation scheme R cannot be used to refer to tuples of R. Which one of the following choices is correct?Q84.
The following functional dependencies hold for relations R(A, B, C) and S(B, D, E) B \rightarrowA, A \rightarrowC The relation R contains 200tuples and the relation S contains 100tuples. What is the maximum number of tuples possible in the natural join R\Join S?Q85.
Consider the following relation schemas : b-Schema = (b-name, b-city, assets) a-Schema = (a-num, b-name, bal) d-Schema = (c-name, a-number) Let branch, account and depositor be respectively instances of the above schemas. Assume that account and depositor relations are much bigger than the branch relation. Consider the following query: \Pi _{c-name}(\sigma _{b-city="Agra" \wedge bal \lt 0} (branch \Join (account \Join depositor))) Which one of the following queries is the most efficient version of the above query ?Q86.
Consider the join of a relation R with a relation S. If R has m tuples and S has n tuples then the maximum and minimum sizes of the join respectively areQ87.
Consider a relation R( A, B, C, D, E ) with the following three functional dependencies.AB \rightarrow C;BC \rightarrow D; C \rightarrow E; The number of superkeys in the relation R is .Q88.
Immunity of the external schemas (or application programs) to changes in the conceptual scheme is referred to as:Q89.
Given two union compatible relations R_1(A, B) and R_2 (C, D), what is the result of the operation R_1 \Join_{ A = C \wedge B = D} R_2?Q90.
Given the relations employee (name, salary, dept-no), and department (dept-no, dept-name,address), Which of the following queries cannot be expressed using the basic relational algebra operations \left(\sigma, \pi,\times ,\Join, \cup, \cap,-\right)?