DBMS MCQs with Answers and Explanations

Question #221

Which clause must be used instead of WHERE to filter or restrict rows after an aggregation or group-by operation has been performed?

A. WHEN

B. WHERE CURRENT OF

C. HAVING

D. RESTRICT

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Correct Answer: Option C

Explanation:
The HAVING clause was added to SQL because the WHERE keyword cannot be applied to aggregate functions; it filters groups generated by the GROUP BY clause.

This question belongs to: Computer Database Management System (DBMS)

Question #222

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Which clause is used in SQL to sort the final query result set in ascending or descending order?

A. SORT BY

B. ORDER BY

C. ARRANGE BY

D. GROUP BY

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Correct Answer: Option B

Explanation:
The ORDER BY clause is used to sort the result set of a query in either ascending (default) or descending (using DESC) order.

This question belongs to: Computer Database Management System (DBMS)

Question #223

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What is the default sorting order when using the ORDER BY clause in an SQL statement?

A. Descending

B. Random

C. Ascending

D. Alphabetic only

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Correct Answer: Option C

Explanation:
By default, the ORDER BY clause sorts the query results in ascending order unless specified otherwise using the DESC keyword.

This question belongs to: Computer Database Management System (DBMS)

Question #224

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Which of the following is NOT an aggregate function in standard SQL?

A. AVG()

B. LENGTH()

C. COUNT()

D. SUM()

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Correct Answer: Option B

Explanation:
SUM(), AVG(), and COUNT() are aggregate functions operating on multiple rows, whereas LENGTH() is a scalar function acting on a single text value.

This question belongs to: Computer Database Management System (DBMS)

Question #225

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Which SQL keyword is placed immediately inside a SELECT statement or an aggregate function to eliminate duplicate rows from the output?

A. UNIQUE

B. SINGLE

C. DIFFERENT

D. DISTINCT

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Correct Answer: Option D

Explanation:
The DISTINCT keyword is used to remove all duplicate values or records from the output of an SQL SELECT query.

This question belongs to: Computer Database Management System (DBMS)

Question #226

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Which SQL wildcard character is used to match exactly one single character when using the LIKE operator?

A. Question mark (?)

B. Asterisk (*)

C. Underscore (*)

D. Percentage sign (%)

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Correct Answer: Option C

Explanation:
In SQL pattern matching with the LIKE operator, the underscore (*) represents exactly one single character, while the percent sign (%) matches zero or more characters.

This question belongs to: Computer Database Management System (DBMS)

Question #227

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Which wildcard character is used with the SQL LIKE operator to represent zero, one, or multiple characters?

A. Underscore (_)

B. Ampersand (&)

C. Percentage sign (%)

D. Hash (#)

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Correct Answer: Option C

Explanation:
The percentage sign (%) is used as a wildcard character to match any sequence of zero or more characters in an SQL LIKE string comparison query.

This question belongs to: Computer Database Management System (DBMS)

Question #228

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Which constraint ensures that a column cannot accept or store an unassigned or missing value?

A. DEFAULT

B. UNIQUE

C. CHECK

D. NOT NULL

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Correct Answer: Option D

Explanation:
The NOT NULL constraint explicitly forces a column to always contain a value, preventing blank or NULL entries.

This question belongs to: Computer Database Management System (DBMS)

Question #229

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Which type of integrity constraint ensures that a foreign key value must either match an existing primary key value in the parent table or be NULL?

A. Key Integrity

B. Domain Integrity

C. Entity Integrity

D. Referential Integrity

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Correct Answer: Option D

Explanation:
Referential Integrity ensures that relationships between tables remain consistent, requiring a foreign key to point to a valid existing row in the referenced table.

This question belongs to: Computer Database Management System (DBMS)

Question #230

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Which rule state that 'no component of a primary key can accept a NULL value'?

A. Entity Integrity Rule

B. Referential Integrity Rule

C. Domain Constraint Rule

D. Security Integrity Rule

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Correct Answer: Option A

Explanation:
The Entity Integrity Rule states that a primary key column cannot contain NULL values, ensuring each row can be explicitly identified.

This question belongs to: Computer Database Management System (DBMS)

Question #231

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What value represents missing, unknown, or inapplicable data in a relational database?

A. Blank Space (' ')

B. Zero (0)

C. Void

D. NULL

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Correct Answer: Option D

Explanation:
NULL is a special marker used in SQL to indicate the absence of a value or that the data is missing, unknown, or not applicable.

This question belongs to: Computer Database Management System (DBMS)

Question #232

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Which operator is specifically used to verify whether a column value contains a NULL entry?

A. IS NULL

B. = NULL

C. IN NULL

D. LIKE NULL

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Correct Answer: Option A

Explanation:
Because NULL represents an unknown value, it cannot be compared using the equality operator (=). Instead, the special 'IS NULL' operator must be used.

This question belongs to: Computer Database Management System (DBMS)

Question #233

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Which SQL command deletes all rows from a table without deleting the structural schema, cannot be rolled back easily in some systems, and does not fire delete triggers?

A. TRUNCATE

B. DELETE

C. DROP

D. REMOVE

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Correct Answer: Option A

Explanation:
TRUNCATE is a DDL command that quickly removes all records from a table by deallocating the data pages, bypassing row-level logging and triggers while leaving the table structure intact.

This question belongs to: Computer Database Management System (DBMS)

Question #234

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What is a virtual table that does not physically exist on storage but is defined by an underlying SQL query called?

A. View

B. Index

C. Stored Procedure

D. Trigger

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Correct Answer: Option A

Explanation:
A View is a virtual, logical table derived from the result set of an SQL SELECT query. It behaves like a table but does not store data independently.

This question belongs to: Computer Database Management System (DBMS)

Question #235

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Which database structure is created to drastically speed up the retrieval of rows from a table at the expense of slower data updates?

A. Index

B. Constraint

C. Schema

D. View

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Correct Answer: Option A

Explanation:
An Index is a performance optimization structure created on table columns to search and locate matching rows quickly without performing a full table scan.

This question belongs to: Computer Database Management System (DBMS)

Question #236

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A database object that automatically executes or fires in response to specific events (like INSERT, UPDATE, or DELETE) on a table is known as a what?

A. Cursor

B. Stored Procedure

C. View

D. Trigger

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Correct Answer: Option D

Explanation:
A Trigger is a named database object containing procedural code that automatically runs or fires when a specific DML statement occurs on a designated table.

This question belongs to: Computer Database Management System (DBMS)

Question #237

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The process of organizing a relational database schema to minimize data redundancy and prevent update anomalies is called what?

A. Generalization

B. Aggregation

C. Normalization

D. Denormalization

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Correct Answer: Option C

Explanation:
Normalization is the systematic process of structuring relational database schemas to eliminate redundant data and maintain data integrity through decomposition.

This question belongs to: Computer Database Management System (DBMS)

Question #238

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Which normal form requires that all attributes in a table contain only atomic, indivisible values, and prohibits multi-valued attributes?

A. Second Normal Form (2NF)

B. Third Normal Form (3NF)

C. Boyce-Codd Normal Form (BCNF)

D. First Normal Form (1NF)

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Correct Answer: Option D

Explanation:
A relation is in First Normal Form (1NF) if and only if the domain of every attribute contains only atomic (indivisible) values, and no repeating groups exist.

This question belongs to: Computer Database Management System (DBMS)

Question #239

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To be in Second Normal Form (2NF), a relation must already satisfy First Normal Form (1NF) and must completely eliminate what type of dependency?

A. Functional Dependency

B. Transitive Dependency

C. Partial Dependency

D. Multivalued Dependency

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Correct Answer: Option C

Explanation:
Second Normal Form (2NF) requires that the table is in 1NF and that no non-prime attribute is partially dependent on any candidate key (meaning no partial dependency exists).

This question belongs to: Computer Database Management System (DBMS)

Question #240

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A table is in Third Normal Form (3NF) if it is in 2NF and has absolutely no non-prime attributes that exhibit what type of dependency?

A. Trivial Dependency

B. Partial Dependency

C. Join Dependency

D. Transitive Dependency

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Correct Answer: Option D

Explanation:
Third Normal Form (3NF) requires a relation to be in 2NF with no transitive dependencies, meaning non-prime attributes cannot be determined by other non-prime attributes.

This question belongs to: Computer Database Management System (DBMS)

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