DB QUIZ 1

Which of the following queries will correctly select all rows where the "age" column is between 20 and 30, inclusive, and sorted by "name" in descending order?

• SELECT * FROM users WHERE age >= 20 OR age <= 30 ORDER BY name DESC;

• SELECT * FROM users WHERE age BETWEEN 20 AND 30 ORDER BY name DESC;

• SELECT * FROM users WHERE age >= 20 AND age <= 30 ORDER BY name ASC;

• SELECT * FROM users WHERE age BETWEEN 20 AND 30 ORDER BY name ASC;

What is the output of the following query if the "salary" column contains NULL values?

SELECT COUNT(salary) FROM employees;

• Count of all rows including NULLs

• Count of all rows excluding NULLs

• Count of only NULL values

• Syntax error

Which SQL query will delete only the first 10 rows from a table "orders" with 1000 rows?

• DELETE FROM orders LIMIT 10;

• TRUNCATE orders LIMIT 10;

• DELETE TOP 10 FROM orders;

• REMOVE FROM orders LIMIT 10;

8. What does the following query do?

SELECT * FROM users WHERE name LIKE 'A%' AND age > 30 OR city = 'New York';

• A. Returns users whose name starts with 'A' and age > 30 and live in New York

• B. Returns users whose name starts with 'A' and age > 30 or live in New York

• C. Returns only users from New York

• D. Syntax error

13. What does this query return?

SELECT * FROM orders WHERE product_name LIKE '%phone%';

• Orders containing 'phone' anywhere in the product name

• Orders where the product name starts with 'phone'

• Orders where the product name ends with 'phone'

• Syntax error

Retrieve all employees who are either in the 'Sales' department or have a salary above 50,000 but exclude those whose names start with 'A' and who are not in 'HR':

Select the top 3 highest paid employees, including those with NULL salaries, but order NULLs last:

Insert a new product into the products table, allowing the price to be NULL if not provided:

Update the status of all inactive users to 'active', but only if their last login was in 2023 and their email contains 'gmail.com':

names contain 'John' and only display departments where this average exceeds 40,000: