The entity integrity constraint ensures that:
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Correct answer: (D) No primary key value can be NULL
CIL MT · Computer Science
DBMS & SQL Previous Year Questions
53 DBMS & SQL (Computer Science) questions asked in CIL MT previous year papers, each with the correct answer and explanation. Read them free on UTpaper, or attempt the full papers as timed online tests.
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Which constraint ensures that a foreign key value in one table either matches a primary key in another table or is NULL (if allowed) in DBMS?
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Correct answer: (A) Referential integrity
If a system uses 32-bit virtual addresses and a page size of 4 KB, how many entries are needed in a single-level page table?
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Correct answer: (C) 2²⁰
Which operation in Relational Algebra is used to retrieve specific columns from a relation?
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Correct answer: (B) Projection (π)
A banking transaction commits successfully, but a system crash occurs immediately afterward. Which mechanism ensures durability?
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Correct answer: (D) Redo log
What does each row in a relational table represent?
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Correct answer: (B) Tuple
In paging, the page table is used to:
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Correct answer: (B) Map logical pages to physical frames
Identify the correct option for project operation in relational algebra:
Statement-1: The project operation is a binary operation that returns its argument
relation, with certain tuple left out.
Statement-2: The result of the PROJECT operation can be visualized as a
horizontal partition of the relation into two relations: one has the needed rows (tuples) and contains the result of the operation, and the other contains the discarded rows.
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Correct answer: (D) Statement-1 is False and Statement-2 is False
Which of the following correctly describes an SQL schema?
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Correct answer: (D) An SQL schema is identified by a name, includes an authorization identifier for its owner, and contains descriptors for elements.
Which of the following statements correctly describes Isolation and Transaction Isolation Levels in a database system?
Statement-1: Ensuring the isolation property is the responsibility of a component
of the database system called the concurrency-control system.
Statement-2: The isolation levels may be Serializable, Repeatable read, Read
committed, Read uncommitted and all the isolation levels additionally disallow dirty writes, that is, they disallow writes to a data item that has already been written by another transaction that has not yet committed or aborted.
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Correct answer: (A) Statement-1 is True and Statement-2 is True
Which of the following scenarios best describes a violation of the consistency property?
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Correct answer: (D) A transaction completes but leaves the database in a state where total credits ≠ total debits.
In a circular queue using arrays, the rear is at index 4, front is at index 2, and capacity = 5. Which expression checks if the queue is full?
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Correct answer: (D) ((rear + 1) % capacity == front)
What shape is commonly used to represent an entity in an ER diagram?
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Correct answer: (C) Rectangle
Which of the following statements are TRUE about server and client side scripting in computer networks?
S1: PHP is used for server side scripting S2: HTML is used for database operations S3: CSS is used for server side scripting S4: ASP.NET is used for server side scripting
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Correct answer: (B) Only S1 and S4
Which of the following statements is TRUE?
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Correct answer: (A) The cardinality ratio for a binary relationship specifies the maximum number of relationship instances that an entity can participate in.
Two schedules are said to be ______, if the order of any two conflicting operations is same in both the schedules.
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Correct answer: (A) conflict equivalent
Considering the relation schemas R (A, B, C, D) and S (C, D, E, F), what will be the degree of the resultant relation of the following Relational Algebra expression, where "*" represents the "natural join" operation?
(σc1(ΠA,B,C(R))) * (σc2(ΠC,D,E(S)))
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Correct answer: (D) 5
Which of the following constraints enforces that the value of the primary key cannot be Null?
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Correct answer: (C) Entity integrity constraint
Which of the following relation schema is always in BCNF?
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Correct answer: (D) R(A, B)
Given total number of instances of a resource to be 18, three processes (P1, P2, and P3) and the resource requirement and allocation table are given below. Which of the following orders of process execution forms a safe (deadlock free) sequence?
Process – Max. Need – Current Allocation
P1 – 12 – 7
P2 – 10 – 5
P3 – 5 – 4
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Correct answer: (B) <P3, P1, P2>
Which of the following recurrence relation can be solved using Master theorem?
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Correct answer: (D) T(n) = 2T(n/2) + 1
Which of the following is used to specify whether the existence of an entity depends on its being related to another entity via the relationship type?
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Correct answer: (D) Participation constraint
Logical data independence is the ability to change ______ schema without having to change ______ schema.
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Correct answer: (C) conceptual; external
Which of the following addressing modes is more appropriate for accessing elements of an array?
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Correct answer: (A) Index mode
Consider the following relation schema R and S along with their tuple sets.
R(A, B) = {<a1, b1>, <a2, b1>, <a3, b1>, <a4, b1>, <a1, b2>, <a3, b2>, <a2, b3>, <a3, b3>, <a4, b3>, <a1, b4>, <a2, b4>, <a3, b4>}
S(A) = {a1, a2, a3}
What is the value of T ← R / S, where "/" represents the Relational Algebra "division" operation?
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Correct answer: (C) T(B) = {b1, b4}
Which of the following statements about the "DELETE" command is FALSE?
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Correct answer: (B) It removes tuples as well as the relation (table).
Which of the following statements about "total specialization" constraint is TRUE?
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Correct answer: (B) Every entity in the superclass must be a member of at least one subclass in the specialization.
Considering the process details given in the following table, what will be the completion order of the processes under the policies FCFS and RR (with CPU quantum of 2 time units)?
Process ID – CPU Burst – Arrival Time
P1 – 5 – 3
P2 – 7 – 2
P3 – 5 – 0
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Correct answer: (B) FCFS: P3, P2, P1 and RR: P3, P1, P2
Consider the following relation schema R along with the tuples.
Employee(name, salary) = {<e1, 10000>, <e2, 5000>, <e3, 2500>, <e4, 7500>, <e5, 8900>, <e6, 9800>}
What is the output of following SQL query?
SELECT name, MAX(salary) FROM Employee WHERE salary < (SELECT MAX(salary) FROM Employee);
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Correct answer: (C) <e6, 9800>
The number of elements in a one-dimensional array with lowest and highest index values as −1024 and 1024 is:
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Correct answer: (D) 2049
Consider the process details given in the following table.
Process ID – CPU Burst – Arrival Time – Priority
P0 – 3 – 0 – 1
P1 – 9 – 2 – 4
P2 – 7 – 4 – 3
P3 – 6 – 3 – 2
A new pre-emptive scheduling algorithm is proposed, i.e., the Longest Remaining Time Next (LRTN), wherein ties are broken by giving priority to the process with the highest priority. Calculate the following.
i. Turnaround time for Process P2
ii. Response time for Process P3
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Correct answer: (A) (i) 20, (ii) 6
In clustering index, the number of index entries is same as the number of:
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Correct answer: (D) distinct index field values
Consider the characters and their frequency counts given in the following table.
Character: a, b, c, d, e, f
Frequency (in 1000s): 24, 16, 12, 20, 8, 4
Using the Huffman coding technique, which of the following is the valid code for character 'c'?
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Correct answer: (B) 1110
Which of the following attributes can be considered as composite, single-valued and key attribute?
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Correct answer: (D) Enrollment number
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.
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Correct answer: (D) schema diagram
Consider the following table of arrival time and burst time for three processes P0, P1, P2.
P0: Arrival time 0 s, Burst time 9 s
P1: Arrival time 1 s, Burst time 4 s
P2: Arrival time 2 s, Burst time 9 s
The preemptive shortest job first scheduling algorithm is used. Scheduling is carried out only at arrival or completion of process. The average waiting time for the three process is ________.
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Correct answer: (D) 5 seconds
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.
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Correct answer: (D) event, condition, action
________ Command is used to enable, disable, modify, or drop a constraint in SQL.
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Correct answer: (D) ALTER Table
A ________ of a relation is a set of one or more attributes whose values are guaranteed to identify tuples in the relation uniquely.
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Correct answer: (B) super key
Solve the following recurrence relation:
T(n) = 4T(n/2) + n²
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Correct answer: (B) Θ(n² log n)
_______ includes a query language and commands to insert tuples into, delete tuples from, and modify tuples in the database.
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Correct answer: (B) Data-manipulation language
Solve the following recurrence relation
T(n) = 4T(n/2) + n
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Correct answer: (A) O(n²)
A ______ is the combination of one or more column values in a table that make a row of data unique within the table.
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Correct answer: (D) primary key
Write true (T) / false (F) for each of the following statements:
A. Symbol table is used only in first phase of a compiler.
B. A pretty printer analyses a program and prints it in such a way that the structure of the program becomes early visible.
C. YACC build up LALR parsing table.
D. If a grammar is LALR(1), it is not necessarily SLR(1)
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Correct answer: (D) F T T F
In SQL – the function – avg, min, max, sum, count are called as _______.
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Correct answer: (A) aggregate function
Relations and fields can be renamed in relational algebra using the renaming operator _______.
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Correct answer: (A) ρ (rho)
In Database management system ACID property refers to:
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Correct answer: (C) Atomicity, Consistency, Isolation, and Durability
A Tuple Relational Calculus query is expressed as ________.
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Correct answer: (A) { T | p(T) }
Consider the following relational schema
Sailors(sid, sname, rating, age)
Reserves(sid, bid, day)
Boats(bid, bname, color)
What is the equivalent of following relational algebra query in SQL query
π_sname ((σ_color='red' Boats) ⋈ Reserves ⋈ Sailors)
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Correct answer: (B) SELECT S.sname FROM Sailors S, Reserves R, Boats B WHERE S.sid = R.sid AND R.bid = B.bid AND B.color = 'red'
A relation is in _______ form if every field contains only atomic values, that is, not lists or sets.
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Correct answer: (A) First normal
How to use these CIL MT Computer Science questions
Every question here was asked in a real CIL MT paper; the paper and shift are shown on the card, and the number opens the question on its own page. Try each one before tapping Show answer, then attempt the full CIL MT papers as timed tests to check your speed under exam conditions.