Computer Science - IT MCQs
Topic Notes: Computer Science - IT
<p>MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.</p>
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
501
A key used for data retrieval purposes that is not a primary or candidate key is often called a:
Answer:
Secondary key
A secondary key is an attribute or combination of attributes that is used for indexing and retrieval. Unlike a primary key, its values do not have to be unique. For example, `LastName` could be a secondary key for efficient searching.
502
Report generators in DBMS are utilized to:
Answer:
Both b and c
Report generators are powerful tools within a DBMS that are specifically designed to retrieve requested information from the database and present it in a formatted, readable report, which effectively answers user queries for data.
503
Referential integrity is a rule that the database enforces to ensure relationships between tables remain consistent. It is typically enforced using a:
Answer:
Foreign Key
Referential integrity is the core concept behind foreign keys. It ensures that a value cannot be entered into a foreign key column unless it matches a value in the referenced primary key column of the parent table.
504
Which type of database stores data in two-dimensional tables?
Answer:
Relational
Relational databases organize data into tables, which consist of rows and columns, allowing for flexible relationships between different data sets.
505
The key used to uniquely identify a record in a database table is:
Answer:
Primary key
The primary key is a unique identifier for each record in a database table, ensuring that no two rows are identical.
506
A regular subquery is processed:
Answer:
From the bottom up
In SQL, the innermost subquery is executed first, and its result is used by the outer query, continuing until the outermost query is processed.
507
What is a key difference between a `UNIQUE` constraint and a `PRIMARY KEY` constraint?
Answer:
A `PRIMARY KEY` does not allow NULL values, while a `UNIQUE` constraint can allow one NULL value.
The main difference is that a primary key constraint is a combination of `UNIQUE` and `NOT NULL`. A unique constraint enforces uniqueness but typically allows a single `NULL` value in the column.
508
In the relational model, what is a tuple?
Answer:
A row in a table.
In the formal terminology of the relational model, a row in a table is called a tuple. It represents a single, implicitly structured data item in a table, consisting of a set of attribute values.
509
Denormalization introduces ______ in a controlled manner.
Answer:
Redundancy
The core idea of denormalization is to strategically add redundant data to the database. This is a controlled process designed to improve performance, unlike the uncontrolled redundancy that normalization aims to eliminate.
510
The logical level of data abstraction describes:
Answer:
The entire database structure for a community of users.
The logical level (or conceptual level) describes what data is stored in the database and what relationships exist among that data. It hides the details of physical storage structures and concentrates on describing the entire database.