Mastering Database Management Systems

What is a primary key in a relational database?

• A primary key is a unique identifier for a record in a relational database.

• A primary key can contain duplicate values in a relational database.

• A primary key is a type of foreign key in a relational database.

• A primary key is used to store large amounts of data in a relational database.

Explain the concept of foreign keys and their purpose.

• Foreign keys are used to enforce referential integrity between tables in a relational database.

• Foreign keys are primarily for data encryption.

• Foreign keys are used to store large binary files.

• Foreign keys are used to create indexes on tables.

What is the difference between a primary key and a unique key?

• A unique key can only be used in one table and cannot be referenced by foreign keys.

• A primary key can have duplicate values but must be unique across tables.

• A primary key cannot be null and uniquely identifies records, while a unique key can be null and also enforces uniqueness.

• A primary key can be null and does not enforce uniqueness.

How do you write a basic SELECT statement in SQL?

• SELECT column1, column2 FROM table_name;

• SELECT * FROM table_name;

• SELECT column1, column2 WHERE table_name;

• FROM table_name SELECT column1, column2;

What is the purpose of the WHERE clause in SQL?

• To create new records in the database.

• To join multiple tables together.

• To filter records based on specified conditions.

• To sort records in ascending order.

Define normalization and its importance in database design.

• Normalization is the process of combining all data into a single table.

• Normalization is only necessary for large databases.

• Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.

• Normalization increases data redundancy and decreases performance.

What are the different normal forms in normalization?

• 1NF, 2NF, 3NF, BCNF, 4NF, 5NF

• 1NF, 2NF, 3NF, 4NF, 6NF

• 1NF+, 2NF+, 3NF+, 4NF+, 5NF+

• 1NF, 2NF, 3NF, 4NF, 5NF, 6NF

Explain denormalization and when it might be used.

• Denormalization is used to eliminate redundancy by splitting tables into smaller ones.

• Denormalization is used to improve read performance by combining data from multiple tables into a single table, often in data warehousing.

• Denormalization is primarily used for data security by encrypting sensitive information.

• Denormalization is a process that only applies to relational databases without any performance benefits.

What are some common database security measures?

• User training programs

• Data backups

• Performance monitoring

• Access controls, encryption, regular updates, security audits, firewalls.

How can user authentication enhance database security?

• User authentication enhances database security by restricting access to authorized users only.

• It eliminates the need for data encryption.

• User authentication slows down database performance.

• It allows anyone to access the database freely.