Database Management System
Q61.
Given the following relation instance. \begin{array}{|l|l|l|}\hline \text{X} & \text{Y} & \text{Z} \\\hline \text{1} & \text{4} & \text{2} \\ \text{1} & \text{5} & \text{3} \\ \text{1} & \text{6} & \text{3} \\ \text{3} & \text{2} & \text{2} \\\hline \end{array}Which of the following functional dependencies are satisfied by the instance?Q62.
Consider the schema R=(S,T, U, V) and the dependencies S \rightarrow T, T \rightarrow U, U \rightarrow V and V \rightarrow S. Let R = (R1\text{ and } R2) be a decomposition such that R1 \cap R2 \neq \phi. The decomposition isQ63.
Relation R with an associated set of functional dependencies, F , is decomposed into BCNF. The redundancy (arising out of functional dependencies) in the resulting set of relations is.Q64.
For a database relation R(a, b, c, d), where the domains a, b, c, d include only atomic values, only the following functional dependencies and those that can be inferred from them hold a \rightarrow c b \rightarrow d This relation isQ66.
Consider the relations r(A, B) and s(B, C), where s.B is a primary key and r.B is a foreign key referencing s.B. Consider the query Q:r \Join (\sigma _{B\lt 5}(s)) Let LOJ denote the natural left outer-join operation. Assume that r and s contain no null values. Which one of the following queries is NOT equivalent to Q?Q67.
Consider a join (relation algebra) between relations r(R)and s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R))\ltsize(s(S)), the join will have fewer number of disk block accesses ifQ68.
Consider the following relation P(X, Y, Z), Q(X, Y, T) and R(Y, V): How many tuples will be returned by the following relational algebra query? Answer:______Q69.
What is the optimized version of the relation algebra expression \pi _{A1}(\pi _{A2}(\sigma _{F1}(\sigma_{F2}(r)))) , where A1, A2 are sets of attributes in r with A_{1}\subset A_{2} and F1, F2 are Boolean expressions based on the attributes in r?Q70.
The following relation records the age of 500 employees of a company, where empNo ( indicating the employee number) is the key: empAge(\underline{empNo},age) Consider the following relational algebra expression: \Pi_{empNo}(empAge \Join_{(age > age1)} \rho_{empNo1,age1}(empAge)) What does the above expression generate?