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
4801
What is the purpose of the `AS` keyword in an SQL statement?
Answer:
To create an alias for a table or column.
The `AS` keyword is used to assign a temporary, more readable name (an alias) to a column or table in the result set of a query. This is particularly useful for columns with aggregate functions or for long table names.
4802
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]
4803
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.
4804
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.
4805
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.
4806
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.
4807
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.
4808
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.
4809
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.
4810
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.