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
461
What is a NOT NULL constraint?
Answer:
It ensures that a column must have a value.
The NOT NULL constraint enforces the rule that a column cannot accept NULL values. This means that a value must be provided for that column whenever a new record is inserted or an existing record is updated.
462
A superkey is a:
Answer:
Set of one or more attributes that, taken collectively, allows us to identify uniquely an entity in the entity set.
A superkey is any combination of columns that uniquely identifies a row. A candidate key is a minimal superkey (i.e., a superkey from which no columns can be removed without losing the uniqueness property).
463
The relational model, proposed by E.F. Codd, represents data and relationships among data as a collection of:
Answer:
Tables
The fundamental concept of the relational model is the relation, which is physically represented as a table. Data is stored in two-dimensional tables consisting of rows and columns.
464
Before a table can be in 2NF, it must first be in:
Answer:
1NF
The normal forms are progressive. A table must satisfy the rules of First Normal Form (1NF) before it can be considered for Second Normal Form (2NF).
465
Which command is used to add, delete, or modify columns in an existing table?
Answer:
`ALTER TABLE`
The `ALTER TABLE` command is a DDL statement used to change the structure of an existing table, such as adding a column, dropping a column, or changing a column's data type.
466
Which key uniquely identifies database records without referring to other data?
Answer:
Candidate Key
A candidate key can uniquely identify rows in a table; [cite: 300] [cite_start]one of them is chosen as the primary key. [cite: 301]
467
A key characteristic of a database system is that the data is integrated and:
Answer:
Shared
A fundamental principle of the database approach is that data is a shared resource. It is integrated into a single repository that can be accessed by many different users and applications throughout an organization.
468
The model for a record management system might be:
Answer:
All of above
A record management system is designed to digitally replicate real-world methods of organizing information. Therefore, its logical model could be based on simple structures like a handwritten list, a Rolodex, or a more complex business form.
469
Which SQL keyword is used to sort the result-set of a query in ascending or descending order?
Answer:
`ORDER BY`
The `ORDER BY` clause is used to sort the records in the result set. By default, it sorts in ascending order (`ASC`), but it can be specified to sort in descending order (`DESC`).
470
Which data model uses the concept of 'owners' and 'members' to describe relationships?
Answer:
Network model
In the CODASYL network model, relationships (called sets) are defined between two record types: an 'owner' record type and a 'member' record type. This structure allows for the representation of many-to-many relationships.