Relational Schema
Q1.
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?Q2.
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 .Q3.
Immunity of the external schemas (or application programs) to changes in the conceptual scheme is referred to as: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.
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?Q10.
If D_1,D_2,...D_n are domains in a relational model, then the relation is a table, which is a subset of