DBMS Basics — Set 2
Computers · DBMS मूल बातें · Questions 11–20 of 60
Which component of DBMS is responsible for the metadata or the 'data about data'?
Correct Answer: D. Data Dictionary
A data dictionary stores definitions of database objects such as tables, columns, and constraints. It acts as a centralized repository of information about the database structure. It is used by the DBMS to validate queries and manage access.
What is the process of minimizing data redundancy and dependency by organizing fields and tables?
Correct Answer: A. Normalization
Normalization involves dividing a database into two or more tables and defining relationships between them. Its main goal is to isolate data so that additions or deletions can be made without losing integrity. This process helps in reducing storage space and improving performance.
Which of the following is an example of a NoSQL database?
Correct Answer: C. MongoDB
MongoDB is a popular non-relational database that stores data in flexible, JSON-like documents. Unlike RDBMS, NoSQL databases do not require a fixed table schema. They are often used for handling big data and real-time web applications.
What is 'Data Independence' in a DBMS environment?
Correct Answer: D. The ability to change the schema at one level without changing it at another
Data independence ensures that changes in the database structure do not affect the applications using it. It is categorized into two types: logical data independence and physical data independence. This concept is a key advantage of using a DBMS over a file system.
In the relational model, what is the term for a table?
Correct Answer: A. Relation
In formal relational database theory, a table is technically called a relation. It is a set of tuples that share the same attributes. This mathematical foundation was originally proposed by E.F. Codd.
What is the maximum number of primary keys a single table can have?
Correct Answer: A. One
Every table in a relational database can have only one primary key. While a primary key can consist of multiple columns (composite key), it still counts as a single primary key. This ensures a unique path to every record in the table.
Which SQL command is used to remove all records from a table without deleting the table structure?
Correct Answer: C. TRUNCATE
The TRUNCATE command quickly deletes all rows in a table while keeping the table definition intact. Unlike the DELETE command, it is generally faster and uses fewer system resources. It cannot be used with a WHERE clause to filter specific rows.
Which of the following describes the 'Isolation' property in ACID?
Correct Answer: D. Transactions are executed as if they are the only ones on the system
Isolation ensures that concurrent transactions do not interfere with each other. It prevents intermediate results of one transaction from being visible to others until it is finished. This is crucial for maintaining data accuracy in multi-user systems.
What is a 'Candidate Key' in a database?
Correct Answer: A. A set of attributes that can uniquely identify a tuple
A candidate key is any column or group of columns that qualifies to be chosen as a primary key. From the set of candidate keys, one is selected as the primary key and the others are called alternate keys. They must contain unique and non-null values.
Which database model represents data as a tree-like structure with parent-child relationships?
Correct Answer: C. Hierarchical Model
The hierarchical model organizes data in a top-down structure, similar to a file system folder hierarchy. Each child node can have only one parent, while a parent can have multiple children. This model was widely used in early mainframe computer systems.