Code for Geniuses

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SQL interview prep

The problems that come up most often in interviews for data roles. Solve them in a real editor and then compare your query with the explained solution.

  1. 💼The second highest salaryReturn the second highest salary in the employees table (a single row and a single column).Easy
  2. 🛒Customers who never boughtShow the name of the customers who have no orders at all.Easy
  3. 📧Duplicate emailsShow each email that appears more than once in customers and how many times it appears.Easy
  4. 🏅The top earner in each departmentShow the department and the name of the person with the highest salary in each department.PROMedium
  5. 📅Month-by-month revenueShow each month (in YYYY-MM format) and its total revenue, sorted from the oldest month to the most recent.PROMedium
  6. 🥇Each customer's first orderShow the name of each customer with orders and the date of their first order.PROMedium
  7. 📈Growth versus the previous monthShow each month and the difference between its revenue and the previous month's (empty in the first month).PROHard