Relational Schema
Q1.
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 .Q2.
Immunity of the external schemas (or application programs) to changes in the conceptual scheme is referred to as:Q3.
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?Q4.
Which one of the options given below refers to the degree (or arity) of a relation in relational database systems?Q5.
Consider the relation R(P,Q,S,T,X,Y,Z,W) with the following functional dependencies. PQ\rightarrow X;\quad P\rightarrow YX;\quad Q\rightarrow Y; \quad Y\rightarrow ZW Consider the decomposition of the relation R into the constituent relations according to the following two decomposition schemes. D1:\quad R=[(P,QS,T);\;(P,T,X);\;(Q,Y);\;(Y,Z,W)] D2:\quad R=[(P,Q,S);\;(T,X);\;(Q,Y);\;(Y,Z,W)] Which one of the following options is correct?Q6.
Considering the following table in a relational database :\begin{array}{|c|c|c|c|} \hline \text { Last Name } & \text { Rank } & \text { Room } & \text { Shift } \\ \hline \text { Smith } & \text { Manager } & 234 & \text { Morning } \\ \hline \text { Jones } & \text { Custodian } & 33 & \text { Afternoon } \\ \hline \text { Smith } & \text { Custodian } & 33 & \text { Evening } \\ \hline \text { Doe } & \text { Clerical } & 222 & \text { Morning } \\ \hline \end{array}According to the data shown in the table, which of the following could be a candidate key of the table?Q9.
If D_1,D_2,...D_n are domains in a relational model, then the relation is a table, which is a subset ofQ10.
Let R=(A,B,C,D,E,F) be a relation scheme with the following dependencies C \rightarrow F, E \rightarrow A, EC \rightarrow D, A \rightarrow B. Which of the following is a key of R?