PRUEBA DE SQL MASTERY

What is a JOIN in SQL and how does it work?

• A JOIN in SQL is used to delete rows from two or more tables based on a related column between them.

• A JOIN in SQL is used to update rows from two or more tables based on a related column between them.

• A JOIN in SQL is used to insert rows from two or more tables based on a related column between them.

• A JOIN in SQL is used to combine rows from two or more tables based on a related column between them. It works by matching the values in the specified columns of the tables being joined and producing a result set that contains columns from both tables.

Explain the importance of indexes in SQL databases.

• Indexes have no impact on query performance in SQL databases

• Indexes in SQL databases are important for improving query performance and optimizing database operations.

• Indexes are only used for sorting data in SQL databases

• Indexes are used for storing images in SQL databases

Give an example of a complex SQL query involving multiple tables.

• SELECT * FROM users, orders WHERE users.id = orders.user_id;

• SELECT users.name, orders.product FROM users JOIN orders ON users.id = orders.user_id;

• SELECT users.name, orders.product FROM users INNER JOIN orders ON users.id = orders.user_id WHERE orders.quantity > 10;

• SELECT users.name, orders.product FROM users LEFT JOIN orders ON users.id = orders.user_id;

What is normalization in the context of SQL databases?

• Normalization involves increasing dependency between data in SQL databases

• Normalization in SQL databases is the process of organizing data efficiently by reducing redundancy and dependency.

• Normalization is the process of adding redundancy to data in SQL databases

• Normalization is not necessary in SQL databases

Explain the concept of transactions in SQL.

• Transactions in SQL are only used for reading data

• Transactions in SQL are a way to ensure data integrity by grouping one or more SQL statements into a single unit of work that either all succeed or all fail.

• Transactions in SQL are a way to delete all data in a database

• Transactions in SQL are used to store images in a database

How are views used in SQL databases and what are their benefits?

• Views in SQL databases are used to create physical tables, simplify data retrieval, enhance security, reduce redundancy, improve query performance.

• Views in SQL databases are used to save complex queries as virtual tables, simplify data retrieval, enhance security, reduce redundancy, improve query performance.

• Views in SQL databases are used to update data in real-time, complicate data storage, enhance security, increase redundancy, degrade query performance.

• Views in SQL databases are used to delete data permanently, complicate data retrieval, reduce security, increase redundancy, degrade query performance.

What are the different types of JOINs in SQL?

• SELF JOIN

• CROSS JOIN

• INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN

• OUTER JOIN

Why is it important to optimize queries in SQL?

• Optimizing queries in SQL has no impact on database performance

• Optimizing queries in SQL increases response time

• Optimizing queries in SQL consumes more resources

• Optimizing queries in SQL improves database performance, reduces response time, minimizes resource consumption, and enhances overall system efficiency.

Discuss the process of database normalization and its different forms.

• Database normalization is the process of organizing a database to reduce redundancy and dependency by dividing large tables into smaller ones and defining relationships between them. There are different normal forms to achieve this, such as 1NF, 2NF, 3NF, BCNF, and 4NF, each with specific rules to ensure data integrity and efficiency.

• Database normalization forms include 5NF, 6NF, and 7NF.

• Database normalization only involves dividing tables into smaller ones without defining relationships.

• Database normalization is the process of adding redundancy to a database to improve performance.

What are the ACID properties in database transactions?

• Atomicity, Consistency, Isolation, Durability

• Atomicity, Consistency, Integration, Durability

• Atomicity, Consistency, Isolation, Volatility

• Atomicity, Inconsistency, Isolation, Durability