ER and Relational Models

    Students(rollno: integer, sname: string)
    Courses(courseno: integer, cname: string)
    Registration(rollno: integer, courseno: integer, percent: real)

      "Find the distinct names of all students who score 
       more than 90% in the course numbered 107"

Given the basic ER and relational models, which of the following is INCORRECT?

Suppose (

A

, B) and (

C

,D) are two relation schemas. Let r1 and r2 be the corresponding relation instances. B is a foreign key that refers to C in r2. If data in r1 and r2 satisfy referential integrity constraints, which of the following is ALWAYS TRUE?

Consider the following relations A, B, C. How many tuples does the result of the following relational algebra expression contain? Assume that the schema of A U B is the same as that of A. 

Table A
Id   Name    Age
----------------
12   Arun    60
15   Shreya  24
99   Rohit   11

Table B
Id   Name   Age
----------------
15   Shreya  24
25   Hari    40
98   Rohit   20
99   Rohit   11

Table C
Id   Phone  Area
-----------------
10   2200   02  
99   2100   01

Consider a relational table r with sufficient number of records, having attributes A1, A2,…, An and let 1 <= p <= n. Two queries Q1 and Q2 are given below.



The database can be configured to do ordered indexing on Ap or hashing on Ap. Which of the following statements is TRUE?

Which of the following tuple relational calculus expression(s) is/are equivalent to  

1) Let R and S be two relations with the following schema R (P,Q,R1,R2,R3) S (P,Q,S1,S2) Where {P, Q} is the key for both schemas. Which of the following queries are equivalent?

Consider the following ER diagram. The minimum number of tables needed to represent M, N, P, R1, R2 is

Consider the data given in above question. Which of the following is a correct attribute set for one of the tables for the correct answer to the above question?

Information about a collection of students is given by the relation studinfo(studId, name, sex). The relation enroll(studId, courseId) gives which student has enrolled for (or taken) that course(s). Assume that every course is taken by at least one male and at least one female student. What does the following relational algebra expression represent?