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
421
A key that is an alternative to the primary key is known as a(n):
Answer:
Alternate key
An alternate key is a candidate key that was not chosen to be the primary key. A table can have multiple candidate keys, but only one is selected as the primary key; the rest are alternate keys.
422
Which normal form deals with the elimination of partial dependencies?
Answer:
Second Normal Form (2NF)
A table is in Second Normal Form (2NF) if it is in 1NF and every non-prime attribute is fully functionally dependent on the primary key. This process specifically removes partial dependencies, where an attribute depends on only a part of a composite primary key.
423
The primary key of a weak entity is composed of the primary key of the strong entity and the weak entity's:
Answer:
Discriminator (or partial key)
A weak entity cannot be identified by its attributes alone. Its primary key is a composite key formed by the primary key of its owner (strong) entity and its own partial key, known as the discriminator.
424
Which of the following is a disadvantage of the hierarchical model?
Answer:
It is difficult to represent many-to-many relationships.
The strict parent-child (one-to-many) structure of the hierarchical model makes it inherently difficult and inefficient to represent many-to-many relationships. Implementing such relationships often requires creating redundant data.
425
The logical design of the database, which describes the data, relationships, and constraints, is called the:
Answer:
Conceptual Schema
The conceptual schema, also known as the logical schema, provides a high-level description of the entire database. It defines the structure, entities, relationships, and constraints for the whole organization.
426
The `INSERT`, `UPDATE`, and `DELETE` commands are all part of which SQL sub-language?
Answer:
DML
These three commands are the core of the Data Manipulation Language (DML), as they are used to add, modify, and remove data from database tables.
427
A 'deletion anomaly' is when:
Answer:
Deleting a row causes other, unrelated information to be lost.
A deletion anomaly occurs when the deletion of a set of data about one entity inadvertently causes the loss of data about a completely different entity. For example, if deleting the last student enrolled in a course also deletes the course information itself.
428
Which normal form is often considered sufficient for most practical database designs?
Answer:
3NF
For the majority of business applications, achieving Third Normal Form (3NF) provides an optimal balance between reducing data redundancy, preventing anomalies, and avoiding the complexity of higher normal forms. BCNF is also common, but 3NF is a widely accepted standard.
429
A table is in First Normal Form (1NF) if:
Answer:
It has no repeating groups or multi-valued attributes.
The core rule for 1NF is that every column in a table must hold atomic (indivisible) values, and each row must be unique. This means no multi-valued attributes, such as a single 'PhoneNumber' column containing multiple phone numbers.
430
The ability of a DBMS to enforce rules, such as ensuring an 'age' column only contains positive numbers, is called:
Answer:
Data Integrity
Data integrity refers to the maintenance of, and the assurance of the accuracy and consistency of, data over its entire life-cycle. A DBMS enforces integrity through constraints.