Consider a relational table with a single record for each enrolled student with the following attributes1. Eno: Unique enrollment number for each enrolled student2. UID: Unique identity number at the national level for each citizen3. Acc_no: 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 student5. Phone: Phone number of the studentWhich of the following options is incorrect?

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 U UID is also a super key

Given two relations R1(A, B) and R2(C, D), the result of following querySelect distinct A, Bfrom R1, R2is guaranteed to be same as R1 provided one of the following condition is satisfied.

R1 has no duplicates and R2 is non-empty.

R1 has no duplicates and R2 is empty.

R1 has no duplicates and R2 is non-empty.

Both R1 and R2 have no duplicates.

R2 has no duplicates and R1 is non - empty

Consider the following schema :Sailors(sid, sname, rating, age)Boats(bid, bname, colour)Reserves(sid, bid, day)Two boats can have the same name but the colour differentiates them.The two relationsρ(Tempsids, (πsid, bid Reserves) / (πbid (σname = ‘Ganga' Boats))),πsname (Tempsids ⋈ Sailors)If / is division operation, the above set of relations represents the query

Names of sailors who have not reserved any Ganga boat

Names of sailors who have reserved all boats called Ganga

Names of sailors who have not reserved any Ganga boat

Names of sailors who have reserved at least one Ganga boat

Names of sailors who have reserved at most one Ganga boat

In context of a relation in database, choose a false statement:

There can be more than one super keys.

A candidate key is a minimal super key.

One of the candidate keys is designated as primary key.

Primary key is obtained by removing one or more attributes from a candidate key.

Consider the following relation.Cinema (theater, address, capacity)Which of the following options will be needed at the end of the SQL querySELECT P1.addressFROM Cinema P1such that it always finds the addresses of theaters with maximum capacity?

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) from Cinema P2)

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

An instance of relational schema R(A, B, C) has distinct values of A including NULL values. Which one of the following is true?

Both "A is a candidate key" and "A is a primary key"

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 has same number of tuples

Given the following schema:employees(emp-id, first-name, last-name, hire-date,dept-id, salary)departments(dept-id, dept-name, manager-id, location-id)You want to display the last names and hire dates of all latest hires in their respective departmentsin the location ID 1700. You issue the following query:SQL>SELECT last-name, hire-dateFROM employeesWHERE (dept-id, hire-date) IN(SELECT dept-id, MAX(hire-date)FROM employees JOIN departments USING(dept-id)WHERE location-id = 1700GROUP BY dept-id);What is the outcome?

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.

On the basis of above given table structures, retrieve the distinct employee ID (EMPID) of all employees of university who are working on project No.20, 30 and 40.

SELECT DISTINCT EMPIDFROM PROJECTWORKWHERE PROJNO=20, 30, 40;

SELECT EMPIDFROM PROJECTWORKWHERE PROJNO=(20, 30, 40);

SELECT EMPIDFROM PROJECTWOREKWHERE PROJNO IN (20, 30, 40);

SELECT DISTINCT EMPIDFROM PROJECTWORKWHERE PROJNO IN (20, 30, 40);

SELECT DISTINCT EMPIDFROM PROJECTWORKWHERE PROJNO=20, 30, 40;

Given the relationsemployee (name, salary, deptno) anddepartment (deptno, deptname, address)Which of the following queries cannot be expressed using the basic relational algebra operations (U, -, x, π, σ, p)?

All employees of a given department

Department address of every employee

Employees whose name is the same as their department name

The sum of all employees' salaries

All employees of a given department

Consider the following relational query on the above database:SELECT S.snameFROM Suppliers S WHERE S.sid NOT IN (SELECT C.sidFROM Catalog CWHERE C.pid NOT IN (SELECT P.pidFROM Parts PWHERE P.color ‘blue’))Assume that relations corresponding to the above schema are not empty. Which of the following is the correct interpretation of the above query?

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

Consider the following schema:Emp (Empcode, Name, Sex, Salary, Deptt)A simple SQL query is executed as follows :SELECT Deptt FROM EmpWHERE sex = ‘M’GROUP by DeptHaving avg (Salary) > { select avg (Salary) from Emp}The output will be

Average salary of male employee is the average salary of the organization

Average salary of male employee is less than the average salary of the organization

Average salary of male employee is equal to the average salary of the organization

Average salary of male employees is more than the average salary of the organization

An expression in the domain relational calculus is of the form:

\(\lbrace P(x_1, x_2,..., x_n)|\rbrace\)

\(\lbrace x_1, x_2, ..., x_n | \rbrace\)

\(\lbrace x_1, x_2, ..., x_n | x_1, x_2, ..., x_n \rbrace\)

\(\lbrace | P(x_1, x_2, ..., x_n)\rbrace\)

82 + Mcqs in Structured Query Language in Structured Query Language (SQL) Page 1 McqOptions

1.	Given the following two statements about SQL(a) An SQL query can contain HAVING clause only if it has GROUP BY clause.(b) In an SQL query “SELECT_FROM_WHERE_GROUP BY_HAVING”, HAVING is executed before WHERE.Which of the following is correct?
A.	(a) and (b) are true
B.	(a) is true, (b) is false
C.	(a) is false, (b) is true
D.	(a) and (b) both are false
Answer» C. (a) is false, (b) is true

Discussion

2.	Consider the following statements S1 and S2 about the relational data model:S1: A relation scheme can have at most one foreign key.S2: A foreign key in a relation scheme R cannot be used to refer to tuples of R.Which one of the following choices is correct?
A.	S1 is true and S2 is false.
B.	Both S1 and S2 are true.
C.	Both S1 and S2 are false.
D.	S1 is false and S2 is true.
Answer» D. S1 is false and S2 is true.

Discussion

3.	_______ SQL command changes one or more fields in a record.
A.	LOOK-UP
B.	INSERT
C.	MODIFY
D.	CHANGE
Answer» D. CHANGE

Discussion

4.	Consider the following SQL query:SELECT title, nameFROM EmployeeORDER BY title, name DESC:In output of above query the different titles are listed in ___________ order the names of employees having same title are listed in ___________ order.
A.	Ascending, Ascending
B.	Ascending, Descending
C.	Descending, Ascending
D.	Descending, Descending
Answer» C. Descending, Ascending

Discussion

5.	_______ symbol is used to see every column of a table.
A.	/
B.	_ _
C.	*
D.	!
Answer» D. !

Discussion

6.	Consider a relational table with a single record for each enrolled student with the following attributes1. Eno: Unique enrollment number for each enrolled student2. UID: Unique identity number at the national level for each citizen3. Acc_no: 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 student5. Phone: Phone number of the studentWhich of the following options is incorrect?
A.	Acc_no is candidate key
B.	ENo can be a 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 U UID is also a super key
Answer» B. ENo can be a primary key

Discussion

7.	Consider a relational database containing the following schemes.CataloguesnopnoCostS1P1150S1P250S1P3100S2P4200S2P5250S3P1250S3P2150S3P5300S3P4250 SupplierssnosnamelocationS1M/s Royal furnitureDelhiS2M/s Balaji furnitureBangaloreS3M/s Premium furnitureChennai PartspnoPnamePart_specP1TableWoodP2ChairWoodP3TableSteelP4AlmirahSteelP5AlmirahWood The primary key of each table is indicated by underling the constituent fields.SELECT s.sno, s.snameFROM Suppliers s, Cataloque cWHERE s.sno = c.sno AND Cost > (SELECT AVG (cost)FROM CataloqueWHERE pno = ‘P4’GROUP BY pno);The number of rows returned by the above SQL query is
A.	4
B.	5
C.	0
D.	2
Answer» B. 5

Discussion

8.	Given two relations R1(A, B) and R2(C, D), the result of following querySelect distinct A, Bfrom R1, R2is guaranteed to be same as R1 provided one of the following condition is satisfied.
A.	R1 has no duplicates and R2 is empty.
B.	R1 has no duplicates and R2 is non-empty.
C.	Both R1 and R2 have no duplicates.
D.	R2 has no duplicates and R1 is non - empty
Answer» B. R1 has no duplicates and R2 is non-empty.

Discussion

9.	Consider the following schema :Sailors(sid, sname, rating, age)Boats(bid, bname, colour)Reserves(sid, bid, day)Two boats can have the same name but the colour differentiates them.The two relationsρ(Tempsids, (πsid, bid Reserves) / (πbid (σname = ‘Ganga' Boats))),πsname (Tempsids ⋈ Sailors)If / is division operation, the above set of relations represents the query
A.	Names of sailors who have reserved all boats called Ganga
B.	Names of sailors who have not reserved any Ganga boat
C.	Names of sailors who have reserved at least one Ganga boat
D.	Names of sailors who have reserved at most one Ganga boat
Answer» B. Names of sailors who have not reserved any Ganga boat

Discussion

10.	A minimal super key (i.e., one of the super keys for which no proper subset is a super key) is called:
A.	Super Key
B.	Candidate Key
C.	Primary Key
D.	Both Candidate and Primary Key
Answer» E.

Discussion

11.	In context of a relation in database, choose a false statement:
A.	There can be more than one super keys.
B.	A candidate key is a minimal super key.
C.	One of the candidate keys is designated as primary key.
D.	Primary key is obtained by removing one or more attributes from a candidate key.
Answer» E.

Discussion

12.	Immunity of the external schemas (or application programs) to changes in the conceptual schema is referred to as:
A.	Physical Data Independence
B.	Logical Data Independence
C.	Both 1) and (b)
D.	None of the above
Answer» C. Both 1) and (b)

Discussion

13.	______ command provides a window through which one can see the data of another table.
A.	SELECT
B.	CREATE VIEW
C.	CREATE
D.	All options are wrong
Answer» C. CREATE

Discussion

14.	______ constraint is specified between two relations and is used to maintain the consistency among tuples of the two relations.
A.	Entity integrity
B.	Referential integrity
C.	Primary key
D.	Unique key
Answer» C. Primary key

Discussion

15.	Consider the following relation.Cinema (theater, address, capacity)Which of the following options will be needed at the end of the SQL querySELECT P1.addressFROM Cinema P1such that it always finds the addresses of theaters with maximum capacity?
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) from 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

16.	An instance of relational schema R(A, B, C) has distinct values of A including NULL values. Which one of the following is true?
A.	A is candidate key
B.	A is not a candidate key
C.	A is a primary key
D.	Both "A is a candidate key" and "A is a primary key"
Answer» B. A is not a candidate key

Discussion

17.	Assume that AB → C, C → D and D → A are simultaneously satisfied by a relation r(R). What are the candidate keys of this relation?
A.	AB, CD and AD
B.	AB and CD
C.	AB and DB
D.	ABCD and BC
Answer» D. ABCD and BC

Discussion

18.	Consider the following table in a relational databaseLast NameRankRoomShiftSmithManager234MorningJonesCustodian33MorningSmithCustodian33EveningDoeClerical222MorningAccording to the data shown in the table, which of the following could be a candidate key of the table?
A.	{Last Name}
B.	{Room}
C.	{Shift}
D.	{Room, Shift}
Answer» E.

Discussion

19.	In SQL decimal data type, _______ indicates the maximum number of digits to the right of decimal point.
A.	Float
B.	Scale
C.	Fraction
D.	Precision
Answer» C. Fraction

Discussion

20.	Let relation R2 has a Foreign Key that refers to Primary Key of relation R1. Which of the following operations may cause violation of referential integrity constraints?I: insert into R1II: insert into R2III: delete from R1IV: delete from R2
A.	II and III
B.	I and IV
C.	I, II and III
D.	III and IV
Answer» B. I and IV

Discussion

21.	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 queryQ:
A.	𝜎𝐵<5(𝑟 ⋈ 𝑠)
B.	𝜎𝐵<5(𝑟 𝐿𝑂𝐽 𝑠)
C.	𝑟 𝐿𝑂𝐽 (𝜎𝐵<5(𝑠))
D.	𝜎𝐵<5(𝑟) 𝐿𝑂𝐽 𝑠
Answer» D. 𝜎𝐵<5(𝑟) 𝐿𝑂𝐽 𝑠

Discussion

22.	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 has same number of tuples
Answer» B. R and S have no duplicates

Discussion

23.	Let for any relation R. IR represents operation insert into R and DR represents operation delete from R. Assume that a relation R2 has a foreign key that refers to primary key of another relation R1. Two operations that may cause violation of referential integrity constraints are:
A.	IR1 and IR2
B.	DR1 and DR2
C.	IR1 and DR2
D.	IR2 and DR1
Answer» E.

Discussion

24.	______ clause allows sorting of query results by one or more columns.
A.	DISTINCT
B.	ALL
C.	WHERE
D.	ORDER BY
Answer» E.

Discussion

25.	_______ key must satisfy referential integrity in a relation, while _______ key must satisfy entity integrity.
A.	Candidate, primary
B.	Foreign, primary
C.	Primary, foreign
D.	Foreign, superkey
Answer» C. Primary, foreign

Discussion

26.	Given the following schema:employees(emp-id, first-name, last-name, hire-date,dept-id, salary)departments(dept-id, dept-name, manager-id, location-id)You want to display the last names and hire dates of all latest hires in their respective departmentsin the location ID 1700. You issue the following query:SQL>SELECT last-name, hire-dateFROM employeesWHERE (dept-id, hire-date) IN(SELECT dept-id, MAX(hire-date)FROM employees JOIN departments USING(dept-id)WHERE location-id = 1700GROUP BY dept-id);What is the outcome?
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

27.	On the basis of above given table structures, retrieve the distinct employee ID (EMPID) of all employees of university who are working on project No.20, 30 and 40.
A.	SELECT EMPIDFROM PROJECTWORKWHERE PROJNO=(20, 30, 40);
B.	SELECT EMPIDFROM PROJECTWOREKWHERE PROJNO IN (20, 30, 40);
C.	SELECT DISTINCT EMPIDFROM PROJECTWORKWHERE PROJNO IN (20, 30, 40);
D.	SELECT DISTINCT EMPIDFROM PROJECTWORKWHERE PROJNO=20, 30, 40;
Answer» D. SELECT DISTINCT EMPIDFROM PROJECTWORKWHERE PROJNO=20, 30, 40;

Discussion

28.	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.snameFROM Students as S, Registration as RWHERE R.rollno=S.rollno AND R.courseno=107 AND R.percent >90(II) Πsname(σcourseno=107 percent>90 (Registration Students))(III) {T \| tudents, Registration ( S.rollno=R.rollnoR.courseno=107 R.percent>90 T.sname=S.sname)}(IV) {N> \| ∃SR∃RP ( R, SN> ∈ Students ∧ R, 107, RP>∈ Registration ∧ RP>90)}
A.	I, II, III and IV
B.	I, II and III only
C.	I, II and IV only
D.	II, III and IV only
Answer» B. I, II and III only

Discussion

29.	A ______ is the combination of one or more column values in a table that make a row of data unique within the table.
A.	foreign key
B.	primary key
C.	candidate key
D.	natural key
Answer» D. natural key

Discussion

30.	In SQL, the _______ command is used to recompile view.
A.	CREATE VIEW
B.	COMPILE VIEW
C.	ALTER VIEW
D.	DEFINE VIEW
Answer» D. DEFINE VIEW

Discussion

31.	Consider the following two tables and four queries in SQL.Book (isbn, bname), Stock (isbn, copies)Query 1: SELECT B.isbn, S.copiesFROM Book B INNER JOIN Stock SON B.isbn = S.isbn; Query 2: SELECT B.isbn, S.copiesFROM Book B LEFT OUTER JOIN Stock SON B.isbn = S.isbn;Query 3: SELECT B.isbn, S.copiesFROM Book B RIGHT OUTER JOIN Stock SON B.isbn = S.isbn; Query 4: SELECT B.isbn, S.copiesFROM Book B FULL OUTER JOIN Stock SON B.isbn = S.isbn; Which one of the queries above is certain to have an output that is a superset of the outputsof the other three queries?
A.	Query 1
B.	Query 2
C.	Query 3
D.	Query 4
Answer» E.

Discussion

32.	Let x, y, z, a, b, c be the attributes of an entity set E. If {x}, {x, y}, {a, b}, {a, b, c}, {x, y, z} are superkeys then which of the following are the candidate keys ?
A.	{x, y} and {a, b}
B.	{x} and {a, b}
C.	{x, y, z} and {a, b, c}
D.	{z} and {c}
Answer» C. {x, y, z} and {a, b, c}

Discussion

33.	A ________ of a relation is a set of one or more attributes whose values are guaranteed to identify tuples in the relation uniquely.
A.	super key
B.	key
C.	foreign key
D.	scheme
Answer» B. key

Discussion

34.	In SQL, _______ is an Aggregate function.
A.	SELECT
B.	CREATE
C.	AVG
D.	MODIFY
Answer» D. MODIFY

Discussion

35.	______ SQL command allows to make queries on the database
A.	DELETE
B.	SELECT
C.	CREATE
D.	DROP
Answer» C. CREATE

Discussion

36.	Given the relationsemployee (name, salary, deptno) anddepartment (deptno, deptname, address)Which of the following queries cannot be expressed using the basic relational algebra operations (U, -, x, π, σ, p)?
A.	Department address of every employee
B.	Employees whose name is the same as their department name
C.	The sum of all employees' salaries
D.	All employees of a given department
Answer» D. All employees of a given department

Discussion

37.	Let R = (A, B, C, D, E, F) be a relation scheme with the following dependencies C → F, E → A, EC → D, A → B. Which of the following is a key for R ?
A.	CD
B.	EC
C.	AE
D.	AC
Answer» C. AE

Discussion

38.	A trigger has three parts.The ________ describes the change that activates the trigger.The ________ is a query that is run whenever the trigger is activated.The ________ is the procedure that is executed if the trigger is activated and the condition is true.
A.	event, condition, actor
B.	entity, condition, action
C.	event, condition, action
D.	event, question, action
Answer» D. event, question, action

Discussion

39.	If D1, D2,...,Dn, are domains in a relational model, then the relation is a table, which is a subset of
A.	D1 ⊕ D2 ⊕ .... ⊕ Dn
B.	D1 × D2 × ...× Dn
C.	D1 ∪ D2 ∪ ...∪ Dn
D.	D1 ∩ D2 ∩ ...∩ Dn
Answer» C. D1 ∪ D2 ∪ ...∪ Dn

Discussion

40.	Consider the following relational query on the above database:SELECT S.snameFROM Suppliers S WHERE S.sid NOT IN (SELECT C.sidFROM Catalog CWHERE C.pid NOT IN (SELECT P.pidFROM Parts PWHERE P.color < > ‘blue’))Assume that relations corresponding to the above schema are not empty. Which of the following is the correct interpretation of the above query?
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» E.

Discussion

41.	Consider the following schema:Emp (Empcode, Name, Sex, Salary, Deptt)A simple SQL query is executed as follows :SELECT Deptt FROM EmpWHERE sex = ‘M’GROUP by DeptHaving avg (Salary) > { select avg (Salary) from Emp}The output will be
A.	Average salary of male employee is the average salary of the organization
B.	Average salary of male employee is less than the average salary of the organization
C.	Average salary of male employee is equal to the average salary of the organization
D.	Average salary of male employees is more than the average salary of the organization
Answer» E.

Discussion

42.	In a relational database model, cardinality of a relation means
A.	The number of tuples
B.	The number of tables
C.	The number of attributes
D.	The number of constraints
Answer» B. The number of tables

Discussion

43.	In the following procedureInteger procedure P(X, Y);Integer X, Y;value x;begin K = 5; L = 8; P = x + y;endX is called by value and Y is called by name. If the procedure were invoked by the following program fragment K = 0; L = 0; Z = P(K,L);Then the value Z would be set equal to
A.	5
B.	8
C.	13
D.	0
Answer» C. 13

Discussion

44.	In SQL – the function - avg, min, max, sum, count are called as _______.
A.	aggregate function
B.	adjunct function
C.	set operation
D.	scalar operation
Answer» B. adjunct function

Discussion

45.	_____ attribute is used to restart the numbering in an ordered list.
A.	Type
B.	Order
C.	Start
D.	Number
Answer» D. Number

Discussion

46.	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. What is the key for R ?
A.	{E, F}
B.	{E, F, H}
C.	{E, F, H, K, L}
D.	{E}
Answer» C. {E, F, H, K, L}

Discussion

47.	A _______ is a pictorial depiction of the schema of a database that shows the relations in the database, their attributes, and primary keys and foreign keys.
A.	relational algebra
B.	schema diagram
C.	relational query languages
D.	flow diagram
Answer» C. relational query languages

Discussion

48.	An expression in the domain relational calculus is of the form:
A.	\(\lbrace P(x_1, x_2,..., x_n)\|\rbrace\)
B.	\(\lbrace x_1, x_2, ..., x_n \| < x_1, x_2, ..., x_n >\rbrace\)
C.	\(\lbrace x_1, x_2, ..., x_n \| x_1, x_2, ..., x_n \rbrace\)
D.	\(\lbrace < x_1, x_2, ..., x_n > \| P(x_1, x_2, ..., x_n)\rbrace\)
Answer» E.

Discussion

49.	Let P be a procedure that for some inputs calls itself ( i.e. is recursive ). If P is guaranteed to terminate, which of the following statement(s) must be true?I. P has a local variablell. P has an execution path where it does not call itselfII. P either refers to a global variable or has at least one parameter
A.	I only
B.	II only
C.	III only
D.	II and III only
Answer» E.

Discussion

50.	Consider the following SQL query to retrieve ecode of employees from EMPLOYEE table, whose address contains 'INDIA':SELECT ecodeFROM EMPLOYEEWHERE _________;Which of the following is most suitable to complete the query?
A.	address LIKE '_INDIA_'
B.	address = %INDIA%
C.	address AS '%INDIA_'
D.	address LIKE '%INDIA%'
Answer» E.

Discussion

Explore topic-wise MCQs in Structured Query Language (SQL).

Given the following two statements about SQL(a) An SQL query can contain HAVING clause only if it has GROUP BY clause.(b) In an SQL query “SELECT_FROM_WHERE_GROUP BY_HAVING”, HAVING is executed before WHERE.Which of the following is correct?

Consider the following statements S1 and S2 about the relational data model:S1: A relation scheme can have at most one foreign key.S2: A foreign key in a relation scheme R cannot be used to refer to tuples of R.Which one of the following choices is correct?

_______ SQL command changes one or more fields in a record.

Consider the following SQL query:SELECT title, nameFROM EmployeeORDER BY title, name DESC:In output of above query the different titles are listed in ___________ order the names of employees having same title are listed in ___________ order.

_______ symbol is used to see every column of a table.

Given two relations R1(A, B) and R2(C, D), the result of following querySelect distinct A, Bfrom R1, R2is guaranteed to be same as R1 provided one of the following condition is satisfied.

A minimal super key (i.e., one of the super keys for which no proper subset is a super key) is called:

In context of a relation in database, choose a false statement:

Immunity of the external schemas (or application programs) to changes in the conceptual schema is referred to as:

______ command provides a window through which one can see the data of another table.

______ constraint is specified between two relations and is used to maintain the consistency among tuples of the two relations.

Consider the following relation.Cinema (theater, address, capacity)Which of the following options will be needed at the end of the SQL querySELECT P1.addressFROM Cinema P1such that it always finds the addresses of theaters with maximum capacity?

An instance of relational schema R(A, B, C) has distinct values of A including NULL values. Which one of the following is true?

Assume that AB → C, C → D and D → A are simultaneously satisfied by a relation r(R). What are the candidate keys of this relation?

Consider the following table in a relational databaseLast NameRankRoomShiftSmithManager234MorningJonesCustodian33MorningSmithCustodian33EveningDoeClerical222MorningAccording to the data shown in the table, which of the following could be a candidate key of the table?

In SQL decimal data type, _______ indicates the maximum number of digits to the right of decimal point.

Let relation R2 has a Foreign Key that refers to Primary Key of relation R1. Which of the following operations may cause violation of referential integrity constraints?I: insert into R1II: insert into R2III: delete from R1IV: delete from R2

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 queryQ:

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.

Let for any relation R. IR represents operation insert into R and DR represents operation delete from R. Assume that a relation R2 has a foreign key that refers to primary key of another relation R1. Two operations that may cause violation of referential integrity constraints are:

______ clause allows sorting of query results by one or more columns.

_______ key must satisfy referential integrity in a relation, while _______ key must satisfy entity integrity.

On the basis of above given table structures, retrieve the distinct employee ID (EMPID) of all employees of university who are working on project No.20, 30 and 40.

A ______ is the combination of one or more column values in a table that make a row of data unique within the table.

In SQL, the _______ command is used to recompile view.

Let x, y, z, a, b, c be the attributes of an entity set E. If {x}, {x, y}, {a, b}, {a, b, c}, {x, y, z} are superkeys then which of the following are the candidate keys ?

A ________ of a relation is a set of one or more attributes whose values are guaranteed to identify tuples in the relation uniquely.

In SQL, _______ is an Aggregate function.

______ SQL command allows to make queries on the database

Given the relationsemployee (name, salary, deptno) anddepartment (deptno, deptname, address)Which of the following queries cannot be expressed using the basic relational algebra operations (U, -, x, π, σ, p)?

Let R = (A, B, C, D, E, F) be a relation scheme with the following dependencies C → F, E → A, EC → D, A → B. Which of the following is a key for R ?

A trigger has three parts.The ________ describes the change that activates the trigger.The ________ is a query that is run whenever the trigger is activated.The ________ is the procedure that is executed if the trigger is activated and the condition is true.

If D1, D2,...,Dn, are domains in a relational model, then the relation is a table, which is a subset of

Consider the following schema:Emp (Empcode, Name, Sex, Salary, Deptt)A simple SQL query is executed as follows :SELECT Deptt FROM EmpWHERE sex = ‘M’GROUP by DeptHaving avg (Salary) > { select avg (Salary) from Emp}The output will be

In a relational database model, cardinality of a relation means

In the following procedureInteger procedure P(X, Y);Integer X, Y;value x;begin K = 5; L = 8; P = x + y;endX is called by value and Y is called by name. If the procedure were invoked by the following program fragment K = 0; L = 0; Z = P(K,L);Then the value Z would be set equal to

In SQL – the function - avg, min, max, sum, count are called as _______.

_____ attribute is used to restart the numbering in an ordered list.

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. What is the key for R ?

A _______ is a pictorial depiction of the schema of a database that shows the relations in the database, their attributes, and primary keys and foreign keys.

An expression in the domain relational calculus is of the form:

Consider the following SQL query to retrieve ecode of employees from EMPLOYEE table, whose address contains 'INDIA':SELECT ecodeFROM EMPLOYEEWHERE _________;Which of the following is most suitable to complete the query?

Consider the following SQL query:SELECT title, nameFROM EmployeeORDER BY title, name DESC:In output of above query the different titles are listed in _ order the names of employees having same title are listed in _ order.

_ key must satisfy referential integrity in a relation, while _ key must satisfy entity integrity.

A trigger has three parts.The describes the change that activates the trigger.The is a query that is run whenever the trigger is activated.The is the procedure that is executed if the trigger is activated and the condition is true.