DBMS Basics — Set 6
Computers · DBMS मूल बातें · Questions 51–60 of 60
Which level of data abstraction is closest to the users?
Correct Answer: C. External Level (View Level)
The external or view level allows users to see only the part of the database they need. It hides the complexity of the logical and physical structures. This is the highest level of data abstraction.
In SQL, which command is used to remove a table structure from the database?
Correct Answer: C. DROP
The DROP command is used to delete an entire table along with its data and structure. Unlike DELETE, this action cannot be easily undone. It is a Data Definition Language (DDL) command.
What is the full form of SQL?
Correct Answer: B. Structured Query Language
SQL stands for Structured Query Language. it is the standard language used to communicate with relational databases. SQL allows users to perform various operations like inserting and updating data.
Which property of a transaction ensures that data remains permanent even after a system failure?
Correct Answer: C. Durability
Durability ensures that once a transaction is completed, the changes are saved to the disk. Even if the power goes out, the data will remain safe. This is one of the four essential ACID properties.
Which of the following is NOT a type of database model?
Correct Answer: D. Sequential
Hierarchical, Relational, and Network are classic models used to organize data. 'Sequential' refers to a method of data access, not a structural database model. The relational model is the most common today.
What is a 'Database Administrator' (DBA) responsible for?
Correct Answer: B. Managing and maintaining the database system
The DBA is a person responsible for the installation, configuration, and security of the database. They ensure that the system is running smoothly and that backups are taken regularly. They also manage user permissions and performance.
Which SQL clause is used to sort the results of a query?
Correct Answer: C. ORDER BY
The ORDER BY clause is used to sort the data in ascending or descending order. By default, it sorts in ascending order. It is usually the last part of a SELECT statement.
In an ER diagram, an 'Attribute' is typically represented by which shape?
Correct Answer: B. Ellipse (Oval)
Attributes in ER diagrams are shown as ellipses or ovals. Entities are shown as rectangles, and relationships are shown as diamonds. This visual language helps in designing database structures.
Which type of database is designed to store data in pairs of keys and values?
Correct Answer: B. Key-Value Database
A key-value database is a type of NoSQL database. It stores data as a collection of key-value pairs where each key is unique. Examples include Redis and DynamoDB.
What is a 'Transaction' in a database?
Correct Answer: B. A logical unit of work performed on the data
A transaction is a series of operations performed as a single logical unit of work. It must be completed entirely to maintain data consistency. For example, transferring money from one bank account to another is a transaction.