MCQ2 marks
Consider a relational database schema with two relations and .
Let be a tuple relational calculus expression.
Which one of the following relational algebraic expressions is equivalent to ?
Single correct
MCQ2 marks
Consider two relations describing and in a sports league:
• : , are team-id and team-name, respectively
• : , , and denote player-id, player-name and the team-id of the player, respectively
Which ONE of the following tuple relational calculus queries returns the name of the players who play for the team having as 'MI'?
Single correct
NAT1 mark
Consider the following two relations, and shown in the figure.
The total number of tuples obtained by evaluating the following expression
is __________
Numerical answer
MCQ2 marks
The relation schema,
Person(pid, city), describes the city of residence for every person uniquely identified by pid. The following relational algebra operators are available: selection, projection, cross product, and rename.
To find the list of cities where at least 3 persons reside, using the above operators, the minimum number of cross product operations that must be used isSingle correct
MCQ1 mark
Which one of the options given below refers to the degree (or arity) of a relation in relational database systems?
Single correct
Answer key coming soon
MSQ1 mark
Consider the following three relations in a relational database.
Which of the following relational algebra expressions return the set of s who own all the brands?
One or more correct
Answer key coming soon
NAT1 mark
A relation in a relational database has 1200 tuples. The attribute has integer values ranging from 6 to 20, and the attribute has integer values ranging from 1 to 20. Assume that the attributes and are independently distributed.
The estimated number of tuples in the output of is __________.
Numerical answer
Answer key coming soon
MCQ2 marks
The following relation records the age of 500 employees of a company, where (indicating the employee number) is the key:
Consider the following relational algebra expression:
What does the above expression generate?
Single correct
Answer key coming soon
NAT2 marks
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?
Numerical answer
MCQ2 marks
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
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?
Single correct
MCQ2 marks
Consider a database that has the relation schemas EMP(EmpId, EmpName, DeptId), and DEPT(DeptName, DeptId). Note that the DeptId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus.
(I)
(II)
(III)
Which of the above queries are safe?
Single correct
Answer key coming soon
NAT2 marks
Consider a database that has the relation schema CR(StudentName, CourseName). An instance of the schema CR is as given below.
CR
StudentName CourseName
SA CA
SA CB
SA CC
SB CB
SB CC
SC CA
SC CB
SC CC
SD CA
SD CB
SD CC
SD CD
SE CD
SE CA
SE CB
SF CA
SF CB
SF CCNumerical answer
Answer key coming soon
MCQ1 mark
SELECT operation in SQL is equivalent to
Single correct
MCQ2 marks
Consider two relations R1(A,B) with the tuples (1,5), (3,7) and R2(A,C) = (1,7), (4,9). Assume that R(A,B,C) is the full natural outer join of R1 and R2. Consider the following tuples of the form (A,B,C): a = (1,5,null), b = (1,null,7), c = (3, null, 9), d = (4,7,null), e = (1,5,7), f = (3,7,null), g = (4,null,9). Which one of the following statements is correct?
Single correct
MCQ2 marks
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))<size(s(S)), the join will have fewer number of disk block accesses ifSingle correct
MCQ1 mark
What is the optimized version of the relation algebra expression , where are sets of attributes in with and are Boolean expressions based on the attributes in ?
Single correct
MCQ2 marks
Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee. Assume that every employee has at least one associated dependent in the dependent relation.
employee (, empName, empAge)
dependent (, depName, depAge)
Consider the following relational algebra query:
The above query evaluates to the set of empIds of employees whose age is greater than that of
Single correct
MCQ2 marks
Consider the following relational schema.
Students(rollno: integer, sname: string)
Courses(courseno: integer, cname: string)
Registration(rollno: integer, courseno: integer, percent: real)
Which of the following queries are equivalent to this query in English?
"Find the distinct names of all students who score more than 90% in the course numbered 107"
(I)
SELECT DISTINCT S.sname
FROM Students as S, Registration as R
WHERE R.rollno=S.rollno AND R.courseno=107 AND R.percent >90Single correct
Answer key coming soon
MCQ2 marks
Suppose and are two relation schemas. Let and be the corresponding relation instances. B is a foreign key that refers to C in . If data in and satisfy referential integrity constraints, which of the following is ALWAYS TRUE?
Single correct
Answer key coming soon
MCQ2 marks
Common data for Q.50 and Q.51: Consider the following relations A, B and C:
How many tuples does the result of the following relational algebra expression contain? Assume that the schema of is the same as that of A.
Single correct
Answer key coming soon
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