Consider a relational table with a single record for each registered student with the following attributes: 1. Registration_Number: Unique registration number for each registered student 2. UID: Unique Identity Number, unique at the national level for each citizen 3. Bank Account_Number: unique account number at the bank. A student can have multiple accounts or joint accounts. This attributes stores the primary account number 4. Name: Name of the Student 5. Hostel_Room: Room number of the hostel Which of the following options is incorrect?

Registration Account_Number can be primary key

Bank Account_Number is a candidate key

Registration Account_Number can be primary key

UID is a candidate key if all students are from the same country

If S is a superkey such that S UID is NULL then S UID is also a super key

Consider the relation Student (Name, sex, marks), where the primary key is shown underlined, pertaining to students in a class that has at least one boy and one girl. What does the following relational algebra expression produce? (Note: p is the rename operator) name (rsex female (student)) - name (studentsex Po , x , m

names of girl students with the highest marks

names of girl students with more marks than some boy student

names of girl students with marks not less than some boy student

names of girl students with more marks than all the boy students

Consider the following log sequence of two transactions on a bank account, with initial balance 12000, that transfer 2000 to a mortagage payment and then apply a 5% interest.

We need not redo log records 2 and 3 because transaction T1 has committed

We must redo log record 6 to set B to 10500

We must redo log record 6 to set B to 10000 and the redo log records 2 and 3.

We need not redo log records 2 and 3 because transaction T1 has committed

We can apply redo and undo operations in arbitrary order because they are idempotent

Consider the relation

Names of employees with a female supervisor

Names of employees with a male supervisor

Names of employees with no immediate male subordinates

Names of employees with no immediate female subordinates

Names of employees with a female supervisor

Information about a collection of students is given by the relation

Courses in which only male students are enrolled

Courses in which all the female students are enrolled

Courses in which a proper subset of female students are enrolled

Courses in which only male students are enrolled

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 if

relation s (S) is in the outer loop.

relation r (R) is in the outer loop.

relation s (S) is in the outer loop.

join selection factor between r (R) and s (S) is more than 0.5.

join selection factor between r (R) and s (S) is less than 0.5.

Consider two relations R

R contains a, b, e, f, g but not c, d.

R contains all of a, b, c, d, e, f, g.

R contains e, f, g but not a, b.

Consider a relation geq which represents greater than or equal to , that is, (x, y) geq only if y x.

The deletion of (x, y) is prohibited

A tupel (z, w) with z > y is deleted

A tuple (z, w) with z > x is deleted

A tuple (z, w) with w < x is deleted

The deletion of (x, y) is prohibited

SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below :

select R.* from R,S where R.a = S.a and is unique R

select distinct R.* from R, S where R.a = S.a

select R.* from R, (select distinct a from S) as S1

select R.* from R,S where R.a = S.a and is unique R

Suppose the adjacency relation of vertices in a graph is represented in a table Adj (X, Y). Which of the following queries cannot be expressed by a relational algebra expression of constant length?

List of all vertices adjacent to a given vertex

List of all vertices which have self loops

List of all vertices which belong to cycles of less than three vertices

List of all vertices reachable from a given vertex

Consider the following relation

WHERE P1. capacity >= Any (select P2. capacity from Cinema P2)

WHERE P1. capacity >= All (select P2. capacity from Cinema P2)

WHERE P1. capacity >= Any (select P2. capacity from Cinema P2)

WHERE P1. capacity > All (select max(P2. capacity) form Cinema P2)

WHERE P1. capacity > Any (select max (P2. capacity) from Cinema P2)

Given relations r(w, x) and s(y, z), the result of select distinct w, x from r, s is guaranteed to be same as r, provided

r has no duplicates and s is non-empty

s has no duplicates and r is non-empty

r and s have the same number of tuples

Assume that, in the suppliers relation above, each supplier and each street within a city has a unique name, and (sname, city) forms a candidate key. No other functional dependencies are implied other than those implied by primary and candidate keys. Which one of the following is true about the above schema?

The schema is in 3NF but not in BCNF

The schema is in 2NF but not in 3NF

Consider the following relational query on the above database :

Find the names of all suppliers who have not supplied a non-blue part

Find the names of all suppliers who have supplied a non-blue part

Find the names of all suppliers who have not supplied a non-blue part

Find the names of all suppliers who have supplied only blue parts

Find the names of all suppliers who have not supplied only blue parts

The employee information in a company is stored in the relation

the average salary is more than the average salary in the company

the average salary of male employees is more than the average salary of all male employees in the company the

average salary of male employees is more than the average salary of employees in the same department

the average salary of male employees is more than the average salary in the company

Title of four most expensive book

Title of fifth most inexpensive book

Titles of fifth most expensive book

Titles of five most expensive book

Consider the set of relations shown below and the SQL query that follows:

Names of students who have got an A grade in all courses taught by Korth

Names of students who have got an A grade in all courses

Names of students who have got an A grade in at least one of the courses taught by Korth

Consider the following relational schemas for a library database:

Both Book and Collection are in 2 NF only

Both Book and Collection are in BCNF

Both Book and Collection are in 3 NF only

Book is in 2 NF and Collection is in 3 NF

Both Book and Collection are in 2 NF only

Consider the following functional dependencies in a database:

in second normal form but not in third normal form

in third normal form but not in BCNF

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

more than zero but less than that of an equivalent 3NF decomposition

Given the following schema: employees (emp-id, first-name, last-name, hire-date, deptid, salary)

It generates an error because of pairwise comparison.

It executes but does not give the correct result.

It executes and gives the correct result.

It generates an error because of pairwise comparison.

It generates an error because the GROUP BY clause cannot be used with table joins in a subquery.

In a database system, unique timestamps are assigned to each transaction using Lamport s logical clock. Let TS( T1) and TS(T2) be the timestamps of transactions T1 and T2 respectively. Besides, T1 holds a lock on the resource R and T2 has requested a conflicting lock on the same resource R. The following algorithm is used to prevent deadlocks in the database system assuming that a killed transaction is restarted with the same timestamp.

The database system is deadlock-free, but not starvation-free.

The database system is both deadlock-free and starvation-free.

The database system is deadlock-free, but not starvation-free.

The database system is starvation-free, but not deadlock-free.

The database system is neither deadlock-free nor starvation-free.

In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on

the size of the blocks, the number of blocks used for the index and the size of the address of the blocks

the size of the blocks, and the size of the address of the blocks

the number of blocks used for the index and the size of the blocks

the size of the blocks, the number of blocks used for the index and the size of the address of the blocks

Which one of the following is a key factor for preferring B+ trees to binary search trees for indexing database relations?

Data transfer from disks is in blocks

Database relations have a large number of records

Database relations are sorted on the primary key

B+ trees require less memory than binary search trees

Data transfer from disks is in blocks

Consider the transactions T1, T2, and T3 and the schedules S1 and S2 given below.

Only S2 is conflict-serializable.

Only S1 is conflict-serializable.

Only S2 is conflict-serializable.

Both S1 and S2 are conflict-serializable.

Neither S1 nor S2 is conflict-serializable.

125 + Mcqs in Database miscellaneous in Database Page 2 McqOptions

51.	Let R and S be relational schemas such that R = {a, b, c} and S = {c}. Now consider the following queries on the database: 1. _{R - S} - _{R - S} ( _{R - S}(r) S - _{r - S , S} (r)) 2. { t \| t _{R - S}(r) u s ( v r ( u = v[s] t = v[ R - S ] ) ) } 3. { t \| t _{R - S}(r) u s ( u s ( u = v[s] t = v[ R - S ] ) ) } 4. Select R.a, R. b From R, S Where R.c = S.c Which of the above queries are equivalent?
A.	1 and 2
B.	1 and 3
C.	2 and 4
D.	3 and 4
Answer» D. 3 and 4

Discussion

52.	Consider a relational table with a single record for each registered student with the following attributes: 1. Registration_Number: Unique registration number for each registered student 2. UID: Unique Identity Number, unique at the national level for each citizen 3. Bank Account_Number: unique account number at the bank. A student can have multiple accounts or joint accounts. This attributes stores the primary account number 4. Name: Name of the Student 5. Hostel_Room: Room number of the hostel Which of the following options is incorrect?
A.	Bank Account_Number is a candidate key
B.	Registration Account_Number can be primary key
C.	UID is a candidate key if all students are from the same country
D.	If S is a superkey such that S UID is NULL then S UID is also a super key
Answer» B. Registration Account_Number can be primary key

Discussion

53.	Consider the relation Student (Name, sex, marks), where the primary key is shown underlined, pertaining to students in a class that has at least one boy and one girl. What does the following relational algebra expression produce? (Note: p is the rename operator) _name (r_{sex female} (student)) - _name (student_sex P_{o , x , m}
A.	names of girl students with the highest marks
B.	names of girl students with more marks than some boy student
C.	names of girl students with marks not less than some boy student
D.	names of girl students with more marks than all the boy students
Answer» E.

Discussion

54.	Consider the following relational schema pertaining to a student s database: Students (Rollno., name, address) Enroll (Rollno., Courseno., coursename) Where the primary keys are shown underlined. The numbers of tuples in the student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum numbers of tuples that can be present in (Student * Enroll), where * denotes natural join?
A.	8, 8
B.	120, 8
C.	960, 8
D.	960, 120
Answer» B. 120, 8

Discussion

55.	Let r be a rational instance with schema R = (A, B, C, D). We define r₁ = _{A, B, C}(r) and r₂ = _{A, D}(r). Let s = r₁ * r₂ where * denotes natural join. Given that the decomposition of r into r₁ and r₂ is lossy, which one of the following is true?
A.	s r
B.	r s = r
C.	r s
D.	r * s = s
Answer» D. r * s = s

Discussion

56.	Which of the following statements are true about an SQL query?
A.	P and R
B.	P and S
C.	Q and R
D.	Q and S
Answer» D. Q and S

Discussion

57.	Consider the following log sequence of two transactions on a bank account, with initial balance 12000, that transfer 2000 to a mortagage payment and then apply a 5% interest.
A.	We must redo log record 6 to set B to 10500
B.	We must redo log record 6 to set B to 10000 and the redo log records 2 and 3.
C.	We need not redo log records 2 and 3 because transaction T1 has committed
D.	We can apply redo and undo operations in arbitrary order because they are idempotent
Answer» C. We need not redo log records 2 and 3 because transaction T1 has committed

Discussion

58.	Let E
A.	2
B.	3
C.	4
D.	5
Answer» C. 4

Discussion

59.	Consider the relation
A.	Names of employees with a male supervisor
B.	Names of employees with no immediate male subordinates
C.	Names of employees with no immediate female subordinates
D.	Names of employees with a female supervisor
Answer» D. Names of employees with a female supervisor

Discussion

60.	Information about a collection of students is given by the relation
A.	Courses in which all the female students are enrolled
B.	Courses in which a proper subset of female students are enrolled
C.	Courses in which only male students are enrolled
D.	None of the above
Answer» C. Courses in which only male students are enrolled

Discussion

61.	Let R and S be two relations with the following schemas.
A.	1 and 2
B.	1 and 3
C.	1, 2 and 3
D.	1, 3 and 4
Answer» E.

Discussion

62.	Let R and S be relational schemas such that R = {a, b, c} and S = {c}. Now consider the following queries on the database:
A.	1 and 2
B.	1 and 3
C.	2 and 4
D.	3 and 4
Answer» D. 3 and 4

Discussion

63.	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 if
A.	relation r (R) is in the outer loop.
B.	relation s (S) is in the outer loop.
C.	join selection factor between r (R) and s (S) is more than 0.5.
D.	join selection factor between r (R) and s (S) is less than 0.5.
Answer» B. relation s (S) is in the outer loop.

Discussion

64.	Consider two relations R
A.	R contains a, b, e, f, g but not c, d.
B.	R contains all of a, b, c, d, e, f, g.
C.	R contains e, f, g but not a, b.
D.	R contains e but not f, g.
Answer» D. R contains e but not f, g.

Discussion

65.	Which of the following is NOT a superkey in a relational schema with attributes V,W, X, Y, Z and primary key V Y?
A.	VXYZ
B.	VWXZ
C.	VWXY
D.	VWXYZ
Answer» C. VWXY

Discussion

66.	Which one of the following is not logically equivalent to x ( y ( ) z ( ) ) ?
A.	x ( z ( ) y ( ) )
B.	x ( z ( ) y ( ) )
C.	x ( y ( ) z ( ) )
D.	x ( y ( ) z ( ) )
Answer» B. x ( z ( ) y ( ) )

Discussion

67.	The minimum number of tables needed to represent M, N, P, R
A.	2
B.	3
C.	4
D.	5
Answer» C. 4

Discussion

68.	Consider a relation geq which represents greater than or equal to , that is, (x, y) geq only if y x.
A.	A tupel (z, w) with z > y is deleted
B.	A tuple (z, w) with z > x is deleted
C.	A tuple (z, w) with w < x is deleted
D.	The deletion of (x, y) is prohibited
Answer» D. The deletion of (x, y) is prohibited

Discussion

69.	SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below :
A.	select distinct R.* from R, S where R.a = S.a
B.	select R.* from R, (select distinct a from S) as S1
C.	where R.a = S1.a
D.	select R.* from R,S where R.a = S.a and is unique R
Answer» D. select R.* from R,S where R.a = S.a and is unique R

Discussion

70.	Suppose the adjacency relation of vertices in a graph is represented in a table Adj (X, Y). Which of the following queries cannot be expressed by a relational algebra expression of constant length?
A.	List of all vertices adjacent to a given vertex
B.	List of all vertices which have self loops
C.	List of all vertices which belong to cycles of less than three vertices
D.	List of all vertices reachable from a given vertex
Answer» E.

Discussion

71.	Consider the following relation
A.	WHERE P1. capacity >= All (select P2. capacity from Cinema P2)
B.	WHERE P1. capacity >= Any (select P2. capacity from Cinema P2)
C.	WHERE P1. capacity > All (select max(P2. capacity) form Cinema P2)
D.	WHERE P1. capacity > Any (select max (P2. capacity) from Cinema P2)
Answer» B. WHERE P1. capacity >= Any (select P2. capacity from Cinema P2)

Discussion

72.	Given relations r(w, x) and s(y, z), the result of select distinct w, x from r, s is guaranteed to be same as r, provided
A.	r has no duplicates and s is non-empty
B.	r and s have no duplicates
C.	s has no duplicates and r is non-empty
D.	r and s have the same number of tuples
Answer» B. r and s have no duplicates

Discussion

73.	Database table by name Loan_Records is given below.
A.	3
B.	9
C.	5
D.
E.	6
Answer» D.

Discussion

74.	How many tuples does the result of the following SQL query contain?
A.	4
B.	3
C.	0
D.	1
Answer» C. 0

Discussion

75.	How many tuples does the result of the following relational algebra expression contain? Assume that the schema of A B is the same as that of A.
A.	7
B.	4
C.	5
D.	9
Answer» B. 4

Discussion

76.	Assume that, in the suppliers relation above, each supplier and each street within a city has a unique name, and (sname, city) forms a candidate key. No other functional dependencies are implied other than those implied by primary and candidate keys. Which one of the following is true about the above schema?
A.	The schema is in BCNF
B.	The schema is in 3NF but not in BCNF
C.	The schema is in 2NF but not in 3NF
D.	The schema is not in 2NF
Answer» B. The schema is in 3NF but not in BCNF

Discussion

77.	Consider the following relational query on the above database :
A.	Find the names of all suppliers who have supplied a non-blue part
B.	Find the names of all suppliers who have not supplied a non-blue part
C.	Find the names of all suppliers who have supplied only blue parts
D.	Find the names of all suppliers who have not supplied only blue parts
Answer» B. Find the names of all suppliers who have not supplied a non-blue part

Discussion

78.	Consider a database table T containing two columns X and Y each of type integer. After the creation of the table, one record (X = 1, Y = 1) is inserted in the table. Let M
A.	127
B.	255
C.	190
D.	257
Answer» B. 255

Discussion

79.	The employee information in a company is stored in the relation
A.	the average salary is more than the average salary in the company
B.	the average salary of male employees is more than the average salary of all male employees in the company the
C.	average salary of male employees is more than the average salary of employees in the same department
D.	the average salary of male employees is more than the average salary in the company
Answer» E.

Discussion

80.	The relation
A.	Title of four most expensive book
B.	Title of fifth most inexpensive book
C.	Titles of fifth most expensive book
D.	Titles of five most expensive book
Answer» E.

Discussion

81.	Consider the set of relations shown below and the SQL query that follows:
A.	Names of students who have got an A grade in all courses taught by Korth
B.	Names of students who have got an A grade in all courses
C.	Names of students who have got an A grade in at least one of the courses taught by Korth
D.	None of the above
Answer» D. None of the above

Discussion

82.	Consider the following relational schemas for a library database:
A.	Both Book and Collection are in BCNF
B.	Both Book and Collection are in 3 NF only
C.	Book is in 2 NF and Collection is in 3 NF
D.	Both Book and Collection are in 2 NF only
Answer» D. Both Book and Collection are in 2 NF only

Discussion

83.	The following functional dependencies hold for relations R(A, B, C) and S(B, D, E)
A.	100
B.	200
C.	300
D.	2000
Answer» B. 200

Discussion

84.	Consider a relational schema R = (A, B, C, D, E, H) on which the following functional dependencies hold: {A B, BC D, E C, D A}. What are the candidate keys of R?
A.	AE, BE
B.	AE, BE, DE
C.	AEH, BEH, BCH
D.	AEH, BEH, DEH
Answer» E.

Discussion

85.	R(A, B, C, D) is a relation. Which of the following does not have a lossless join, dependency preserving BCNF decomposition?
A.	A B, B CD
B.	A B, B C, C D
C.	AB C, C AD
D.	A BCD
Answer» D. A BCD

Discussion

86.	Consider the following functional dependencies in a database:
A.	in second normal form but not in third normal form
B.	in third normal form but not in BCNF
C.	in BCNF
D.	none of the above
Answer» E.

Discussion

87.	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
A.	zero
B.	more than zero but less than that of an equivalent 3NF decomposition
C.	proportional to the size of F
D.	indetermine
Answer» B. more than zero but less than that of an equivalent 3NF decomposition

Discussion

88.	Relation R is decomposed using a set of functional dependencies F, and relation S is decomposed using another set of functional dependencies G. One decomposition is definitely BCNF, the other is definitely 3NF, but it is not known which is to make a guaranteed identification, which one of the following tests should be used on the deocmpositions? (Assume that the closures of F and G are available).
A.	Dependency-preservation
B.	Lossless-join
C.	BCNF definition
D.	3NF definition
Answer» D. 3NF definition

Discussion

89.	Given the following statements: S1: A foreign key declaration can always be replaced by an equivalent check assertion in SQL. S2: Given the table R(a,b,c) where a and b together form the primary key, the following is a valid table definition.
A.	S1 is TRUE and S2 is FALSE.
B.	Both S1 and S2 are TRUE.
C.	S1 is FALSE and S2 is TRUE.
D.	Both S1 and S2 are FALSE.
Answer» E.

Discussion

90.	Consider the relation scheme R = (E, F, G, H, I, J, K, L, M, N) and the set of functional dependencies {{E, F} {G}, {F} {I, J}, {E, H} {K, L}, {K} {M}, {L} {N}} on R.
A.	{E, F}
B.	{E, F, H}
C.	{E, F, H, K, L}
D.	{E}
Answer» C. {E, F, H, K, L}

Discussion

91.	Given the following schema: employees (emp-id, first-name, last-name, hire-date, deptid, salary)
A.	It executes but does not give the correct result.
B.	It executes and gives the correct result.
C.	It generates an error because of pairwise comparison.
D.	It generates an error because the GROUP BY clause cannot be used with table joins in a subquery.
Answer» C. It generates an error because of pairwise comparison.

Discussion

92.	The relational schema Student Performance (name, coureNo., rollNo., grade) has the following functional dependencies
A.	2NF
B.	3NF
C.	BCNF
D.	4NF
Answer» C. BCNF

Discussion

93.	In a database system, unique timestamps are assigned to each transaction using Lamport s logical clock. Let TS( T1) and TS(T2) be the timestamps of transactions T1 and T2 respectively. Besides, T1 holds a lock on the resource R and T2 has requested a conflicting lock on the same resource R. The following algorithm is used to prevent deadlocks in the database system assuming that a killed transaction is restarted with the same timestamp.
A.	The database system is both deadlock-free and starvation-free.
B.	The database system is deadlock-free, but not starvation-free.
C.	The database system is starvation-free, but not deadlock-free.
D.	The database system is neither deadlock-free nor starvation-free.
Answer» B. The database system is deadlock-free, but not starvation-free.

Discussion

94.	A B
A.	16
B.	42
C.	43
D.	44
Answer» D. 44

Discussion

95.	Consider a B
A.	1
B.	2
C.	3
D.	4
Answer» C. 3

Discussion

96.	In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on
A.	the size of the blocks, and the size of the address of the blocks
B.	the number of blocks used for the index and the size of the blocks
C.	the size of the blocks, the number of blocks used for the index and the size of the address of the blocks
D.	None of the above
Answer» C. the size of the blocks, the number of blocks used for the index and the size of the address of the blocks

Discussion

97.	Consider a relational table r with sufficient number of records, having attributes A
A.	Only a
B.	Only b
C.	Both a and b
D.	None of the above
Answer» D. None of the above

Discussion

98.	Which one of the following is a key factor for preferring B+ trees to binary search trees for indexing database relations?
A.	Database relations have a large number of records
B.	Database relations are sorted on the primary key
C.
D.	B+ trees require less memory than binary search trees
E.	Data transfer from disks is in blocks
Answer» E. Data transfer from disks is in blocks

Discussion

99.	The order of a leaf node in a B
A.	63
B.	64
C.	67
D.	68
Answer» B. 64

Discussion

100.	Consider the transactions T1, T2, and T3 and the schedules S1 and S2 given below.
A.	Only S1 is conflict-serializable.
B.	Only S2 is conflict-serializable.
C.	Both S1 and S2 are conflict-serializable.
D.	Neither S1 nor S2 is conflict-serializable.
Answer» B. Only S2 is conflict-serializable.

Discussion

Explore topic-wise MCQs in Database.

Let r be a rational instance with schema R = (A, B, C, D). We define r1 = A, B, C(r) and r2 = A, D(r). Let s = r1 * r2 where * denotes natural join. Given that the decomposition of r into r1 and r2 is lossy, which one of the following is true?

Which of the following statements are true about an SQL query?

Consider the following log sequence of two transactions on a bank account, with initial balance 12000, that transfer 2000 to a mortagage payment and then apply a 5% interest.

Let E

Consider the relation

Information about a collection of students is given by the relation

Let R and S be two relations with the following schemas.

Let R and S be relational schemas such that R = {a, b, c} and S = {c}. Now consider the following queries on the database:

Consider two relations R

Which of the following is NOT a superkey in a relational schema with attributes V,W, X, Y, Z and primary key V Y?

Which one of the following is not logically equivalent to x ( y ( ) z ( ) ) ?

The minimum number of tables needed to represent M, N, P, R

Consider a relation geq which represents greater than or equal to , that is, (x, y) geq only if y x.

SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below :

Suppose the adjacency relation of vertices in a graph is represented in a table Adj (X, Y). Which of the following queries cannot be expressed by a relational algebra expression of constant length?

Consider the following relation

Given relations r(w, x) and s(y, z), the result of select distinct w, x from r, s is guaranteed to be same as r, provided

Database table by name Loan_Records is given below.

How many tuples does the result of the following SQL query contain?

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

Consider the following relational query on the above database :

Consider a database table T containing two columns X and Y each of type integer. After the creation of the table, one record (X = 1, Y = 1) is inserted in the table. Let M

The employee information in a company is stored in the relation

The relation

Consider the set of relations shown below and the SQL query that follows:

Consider the following relational schemas for a library database:

The following functional dependencies hold for relations R(A, B, C) and S(B, D, E)

Consider a relational schema R = (A, B, C, D, E, H) on which the following functional dependencies hold: {A B, BC D, E C, D A}. What are the candidate keys of R?

R(A, B, C, D) is a relation. Which of the following does not have a lossless join, dependency preserving BCNF decomposition?

Consider the following functional dependencies in a database:

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

Given the following statements: S1: A foreign key declaration can always be replaced by an equivalent check assertion in SQL. S2: Given the table R(a,b,c) where a and b together form the primary key, the following is a valid table definition.

Consider the relation scheme R = (E, F, G, H, I, J, K, L, M, N) and the set of functional dependencies {{E, F} {G}, {F} {I, J}, {E, H} {K, L}, {K} {M}, {L} {N}} on R.

Given the following schema: employees (emp-id, first-name, last-name, hire-date, deptid, salary)

The relational schema Student Performance (name, coureNo., rollNo., grade) has the following functional dependencies

A B

Consider a B

In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on

Consider a relational table r with sufficient number of records, having attributes A

Which one of the following is a key factor for preferring B+ trees to binary search trees for indexing database relations?

The order of a leaf node in a B

Consider the transactions T1, T2, and T3 and the schedules S1 and S2 given below.

Let r be a rational instance with schema R = (A, B, C, D). We define r₁ = _{A, B, C}(r) and r₂ = _{A, D}(r). Let s = r₁ * r₂ where * denotes natural join. Given that the decomposition of r into r₁ and r₂ is lossy, which one of the following is true?