Exploring Database Technologies

What is a relational database management system (RDBMS)?

• A database that uses only XML for data storage.

• A relational database management system (RDBMS) is a system that manages data in a structured format using tables and SQL.

• A system that only stores unstructured data.

• A type of software that manages only images and videos.

Name three popular RDBMS software.

• Oracle Database

• MySQL, PostgreSQL, Microsoft SQL Server

• MongoDB

• SQLite

What is the primary purpose of SQL?

• To manage and manipulate non-relational databases.

• To perform complex mathematical calculations.

• The primary purpose of SQL is to manage and manipulate relational databases.

• To create and design websites.

Explain the concept of normalization in databases.

• Normalization involves encrypting sensitive data for security.

• Normalization is the method of increasing data storage capacity.

• Normalization is the process of backing up data regularly.

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

What is a primary key in a relational database?

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

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

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

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

How can indexing improve SQL query performance?

• Indexing requires more storage space, which decreases performance.

• Indexing improves SQL query performance by allowing faster data retrieval and reducing the need for full table scans.

• Indexing has no effect on query performance and is unnecessary.

• Indexing slows down data retrieval by increasing the amount of data to scan.

What is the difference between INNER JOIN and LEFT JOIN?

• INNER JOIN includes NULL values from the left table.

• LEFT JOIN only returns rows from the right table.

• INNER JOIN returns all rows from both tables.

• INNER JOIN returns matched rows; LEFT JOIN returns all left rows with matched right rows or NULLs.

What are aggregate functions in SQL? Give an example.

• An example of an aggregate function is COUNT, which counts the number of rows in a table. For instance, 'SELECT COUNT(*) FROM employees;' counts all employees in the employees table.

• SUM is used to find the average of a column.

• MAX returns the minimum value in a dataset.

• AVG counts the number of unique values in a column.

What is a subquery and how is it used in SQL?

• A subquery is a command to delete records in SQL.

• A subquery is a type of database index.

• A subquery is a nested query used to provide data to the main query in SQL.

• A subquery is a method to create new tables in SQL.

What strategies can be employed for SQL query optimization?

• Relying solely on default settings

• Ignoring database statistics and metrics

• Using only subqueries for all operations

• Strategies for SQL query optimization include indexing, efficient joins, avoiding SELECT *, analyzing execution plans, and caching.