Mastering SQL: A Comprehensive Quiz

What is the purpose of the `SELECT` statement in SQL?

• To delete data from a database

• To retrieve data from a database

• To update data in a database

• To create a new table in a database

Which of the following is the correct order of database normalisation forms?

• 1NF, 2NF, 3NF, BCNF

• 2NF, 1NF, 3NF, BCNF

• 3NF, 2NF, 1NF, BCNF

• BCNF, 3NF, 2NF, 1NF

Which SQL clause is used to filter records?

• ORDER BY

• GROUP BY

• WHERE

• HAVING

What type of join returns all records from the left table and the matched records from the right table?

• INNER JOIN

• LEFT JOIN

• RIGHT JOIN

• FULL JOIN

Which SQL function is used to count the number of rows in a table?

• SUM()

• AVG()

• COUNT()

• MAX()

What does the SQL command `INSERT INTO` do?

• It updates existing data in a table

• It deletes data from a table

• It adds new data into a table

• It creates a new table

Which of the following is a characteristic of a table in 1NF (First Normal Form)?

• It has no repeating groups

• It has no partial dependencies

• It has no transitive dependencies

• It has a single candidate key

What is the result of the following SQL query: `SELECT * FROM Employees WHERE Salary > 50000;`?

• It selects all employees with a salary less than £50,000

• It selects all employees with a salary greater than £50,000

• It selects all employees with a salary equal to £50,000

• It selects all employees regardless of salary

Which SQL function is used to find the highest value in a column?

• MIN()

• MAX()

• AVG()

• SUM()

What is the purpose of the `UPDATE` statement in SQL?

• To retrieve data from a database

• To delete data from a database

• To modify existing data in a database

• To create a new table in a database