Consider the following relations P(X,Y,Z), Q(X,Y,T) and R(Y,V).

How many tuples will be returned by the following relational algebra query?

A relational database contains two tables Student and Performance as shown below :

The primary key of the Student table is Roll_no. For the Performance table, the columns Roll_no. and Subject_code together from the primary key. Consider the SQL query given below:

SELECT S.Student_name, sum (P.Marks)
       FROM Student S, Performance P
       WHERE P.Marks > 84
       GROUP BY S.Student_name;

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

Let the set of functional dependencies

F = {QR → S, R → P, S → Q}

hold on a relation schema X = (PQRS). X is not in BCNF. Suppose X is decomposed into two schemas Y and Z, where Y = (PR) and Z = (QRS).

Consider the two statements given below.

I. Both Y and Z are in BCNF
II. Decomposition of X into Y and Z is dependency preserving and lossless

Which of the above statements is/are correct?

Which one of the following statements is NOT correct about the B⁺ tree data structure used for creating an index of a relational database table?