Consider a relation R(A, B, C, D, E) with the following three functional dependencies.

AB $$\to$$ C ; BC $$\to$$ D ; C $$\to$$ E;

The number of superkeys in the relation R is _________.

Let R_i(z) and W_i(z) denote read and write operations on a data element z by a transaction T_i, respectively. Consider the schedule S with four transactions.

S : R₄(x), R₂(x), R₃(x), R₁(y), W₁(y), W₂(x), W₃(y), R₄(y)

Which one of the following serial schedules is conflict equivalent to S?

Consider the relational database with the following four schemas and their respective instances.

Student( $$\underline {sNo} $$ , sName, dNo) Dept( $$\underline {dNo} $$ , dName)

Course( $$\underline {cNo} $$ , cName, dNo) Register( $$\underline {sNo} $$ , $$\underline {cNo} $$ )

SQL Query :

SELECT * FROM Student AS S WHERE NOT EXIST

(SELECT cNo FROM Course WHERE dNo = "D01"

EXCEPT

SELECT cNo FROM Register WHERE sNo = S.sNo)

The number of rows returned by the above SQL query is _____________.

Consider two files systems A and B, that use contiguous allocation and linked allocation, respectively. A file of size 100 blocks is already stored in A and also in B. Now, consider inserting a new block in the middle of the file (between 50^th and 51^st block), whose data is already available in the memory. Assume that there are enough free blocks at the end of the file and that the file control blocks are already in memory. Let the number of disk accesses required to insert a block in the midele of the file in A and B are n_A and n_B, respectively, then the value of n_A + n_B is _____________.