SQL Practice Questions

Sharpen your SQL proficiency and elevate your confidence for that upcoming interview or project. Explore a diverse mix of SQL problems that cover a spectrum of complexities. Each question is designed to expand your knowledge and reinforce your understanding of SQL concepts. Explore, learn, and conquer SQL complexities one question at a time!

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From the company table, return the company, founder_net_worth, and a new column called 'rich' which holds the values 'millionaire' if the Founder_net_worth value is less than 1, the value 'billionaire' if the Founder_net_worth value is greater than 1, and 'oops' if the value is anything else.

For each user id return the user age, and a new column called age_category with the value 'over 50' if the user is over 50, '40 to 50' if the user is between 40 and 50 years old, and 'under 40' if the user is under 40 years old.

Calculate ROAS (Return On Ad Spend) for each traffic source within 28 days of user registration. Arrange the result set from largest to smallest ROAS. ROAS = Total Revenue Amount/Total Amount Spent on Advertising.

Using the users that have no transaction history, get each unique traffic source and the total customer acquisition cost per source. Order by the total acquisition cost and replace all NULL values with 0.

Find all pairs of founders who were born in the same year. Exclude records where founders are paired with themselves and return only the first_name, last_name, and dob_year for each founder in a pair.

Using a RIGHT JOIN calculate the difference between the transaction date and registration date for each transaction id. Call this new columns date_diff. Return transaction id and date_diff.

Create a query that computes the initial payment cost, occurring within 7 days from the registration date, categorized by traffic sources. Any division by zero should yield a NULL value.

Find the top 5 passengers who have covered the longest distances. Display their ID, names, and the overall distance traveled, beginning with the passenger who has traveled the farthest.

For each user id, return the country column as well as a new column called is_na which has the value 'Yes' if the user is in the United States (US) or Canada (CA) and 'No' otherwise.

Using a RIGHT JOIN, get the records where a user registered in the United States (US) but payed for a transaction with a currency other than the United States Dollar (USD).