Computer Science/IT MCQs
Topic Notes: Computer Science/IT
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
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
231
What is a structured collection of data enabling easy access and modification?
Answer:
Database
A database organizes data for efficient searching, updating, and management. [cite: 228, 229]
232
Fifth Normal Form (5NF) is designed to handle which type of dependency?
Answer:
Join dependency
Fifth Normal Form (5NF), also known as Project-Join Normal Form (PJ/NF), deals with join dependencies. A table is in 5NF if every non-trivial join dependency is implied by the candidate keys of the table.
233
Normalization helps to achieve a 'lossless join decomposition'. What does this mean?
Answer:
When the decomposed tables are joined back together, the original table is recreated exactly.
A lossless join decomposition is a critical property of normalization. It ensures that when you break a table into multiple smaller tables, you can always reconstruct the original, unnormalized table perfectly by joining the new tables, without creating any spurious (extra) or lost tuples.
234
The function of a database is:
Answer:
To collect and organize input data
The primary and most fundamental function of a database is to act as a structured repository. It is designed to systematically collect input data and organize it in a way that allows for efficient storage, retrieval, and management.
235
Which of the following changes may fail when modifying a database column?
Answer:
Changing a column data type from char to date
This change may fail if the existing character data in the column cannot be validly converted into the date format.
236
What is a composite key?
Answer:
A key that is composed of two or more columns.
A composite key is a primary key that consists of two or more columns. The combination of these columns' values must be unique for each record in the table, even though the individual column values may not be unique.
237
A transitive dependency exists when a non-key attribute is functionally dependent on:
Answer:
Another non-key attribute.
A transitive dependency is an indirect relationship between attributes. If A -> B and B -> C, then there is a transitive dependency C -> A via B, where A is the primary key and B and C are non-key attributes. 3NF aims to remove this.
238
Can a primary key column contain NULL values?
Answer:
No, a primary key must not contain NULL values.
A primary key constraint is a combination of a `NOT NULL` constraint and a `UNIQUE` constraint. Therefore, it is a strict rule that a primary key column cannot have any NULL values.
239
An attribute in one table that is a primary key in another table is a:
Answer:
Foreign Key
This is the definition of a foreign key. It creates a referential link between the two tables.
240
What do you create when you want to ask the database for specific information?
Answer:
Query
A query is a formal request to a database to retrieve, add, modify, or delete data based on specified criteria.