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
431
Which of the following is NOT a component of the Entity-Relationship model?
Answer:
Method
Methods, which represent behavior or operations, are a concept from the object-oriented data model, not the ER model. The ER model focuses on the static structure of data through entities, attributes, and relationships.
432
Which normal form is considered the strictest?
Answer:
Boyce-Codd Normal Form (BCNF)
Boyce-Codd Normal Form (BCNF) is an extension and a stricter version of 3NF. For a table to be in BCNF, for every non-trivial functional dependency X → Y, X must be a superkey. This handles certain rare anomalies that 3NF does not.
433
In a three-tier database architecture, which layer contains the business logic?
Answer:
Application tier
The three-tier architecture consists of a presentation tier (UI), an application tier (business logic), and a data tier (database). The application tier acts as a mediator, processing client requests and handling business rules before interacting with the database.
434
A relational database was first proposed by:
Answer:
E.F. Codd
Edgar F. Codd of IBM published the paper "A Relational Model of Data for Large Shared Data Banks" in 1970, which became the foundation for the relational database model.
435
What does DCL stand for in the context of SQL?
Answer:
Data Control Language
DCL stands for Data Control Language and is used to control access to data within the database. Its main commands are `GRANT` and `REVOKE`.
436
How many copies of the database schema are typically used in a redesign process?
Answer:
Three
In a professional environment, it's common to have three copies: the production (live) schema, a test schema for quality assurance, and a development schema for making changes.
437
Can a primary key be made up of more than one column?
Answer:
Yes, this is called a composite primary key.
Yes, when a single column is not sufficient to uniquely identify a row, two or more columns can be combined to form a composite primary key.
438
What is the primary difference between `UNION` and `UNION ALL`?
Answer:
`UNION ALL` includes duplicates, `UNION` does not.
Both combine result sets, but `UNION` performs a `DISTINCT` operation to remove duplicate rows from the final result set, while `UNION ALL` includes all rows from all queries, including duplicates. `UNION ALL` is faster as it doesn't have to check for duplicates.
439
What does SQL stand for?
Answer:
Structured Query Language
SQL is used to manage and manipulate relational databases.
440
What is the main purpose of a foreign key constraint?
Answer:
To enforce referential integrity between two tables.
The primary purpose of a foreign key is to enforce referential integrity. This means that a value in the foreign key column of one table must match an existing value in the primary key column of the related table, preventing orphaned records.