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
471
Which DCL command would a database administrator use to give a user permission to perform `SELECT` operations on a table?
Answer:
`GRANT SELECT ON table_name TO user;`
The `GRANT` command is the standard DCL statement used to provide specific privileges (like `SELECT`, `INSERT`, `UPDATE`, etc.) on database objects to users or roles.
472
Which constraint ensures that all entries in a specific column must have a value and cannot be left empty?
Answer:
NOT NULL
The `NOT NULL` constraint enforces that a column cannot accept NULL values. This means that a value must be entered for that column when a new record is inserted or an existing record is updated.
473
Which operator combines the result-set of two or more SELECT statements but removes duplicate rows?
Answer:
UNION
The `UNION` operator is used to combine the result sets of two or more SELECT statements. It returns all unique rows selected by each query. `UNION ALL` performs the same function but includes all duplicate rows.
474
What does the 'Isolation' property of ACID guarantee?
Answer:
Transactions are processed in a serialized manner, even if executed concurrently.
Isolation ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed serially, one after the other. It prevents transactions from interfering with each other.
475
A partial dependency, which is eliminated in 2NF, can only exist in tables that have:
Answer:
A composite primary key (a primary key made of two or more attributes).
A partial dependency occurs when a non-key attribute is functionally dependent on only a part of the composite primary key. If the primary key is a single attribute, a partial dependency cannot exist.
476
Which of the following is a DCL command?
Answer:
GRANT
DCL stands for Data Control Language. Its commands are used to control access and grant permissions to database users. GRANT is a DCL command used to give users privileges to access or perform operations on the database.
477
The ascending order of a data hierarchy is:
Answer:
Bit-byte-field-record-file-database
Data is organized in a hierarchy starting from the smallest unit. A bit is the smallest unit, 8 bits form a byte (a character), bytes are grouped into fields (e.g., a name), fields are grouped into a record (e.g., a customer's information), records are collected into a file, and related files form a database.
478
Which of the following is considered a legacy database system based on a pre-relational model?
Answer:
IMS (Information Management System)
IMS is an early hierarchical database management system developed by IBM. It is considered a legacy system, predating the now-dominant relational model used by systems like Oracle and MySQL.
479
Data Warehousing provides:
Answer:
Storage, functionality, and query responsiveness
Data warehouses are optimized for storing vast amounts of data, providing analytical functionality, and responding quickly to complex queries.
480
Which of the following is a procedural language?
Answer:
Relational Algebra
Relational algebra is a procedural query language. It provides a set of operations that take one or two relations as input and produce a new relation as their result. The user specifies the steps or procedures to get the required result.