In-memory databases Code Challenges & Tips

1. Write a SQL query to select all records from a table named `Users` where the `last_login` date is within the last 30 days.

2. Create a stored procedure that accepts a user ID and returns all orders placed by that user from the `Orders` table.

3. Write a SQL command to create a unique index on the `email` column of the `Customers` table.

4. Implement a simple caching mechanism in code using an in-memory database to track the top 5 most frequently accessed items.

5. Write a function that retrieves all users from the `Users` table who are currently active and orders them by their registration date in descending order.

6. Write a SQL query to perform a left join between the `Users` and `Orders` tables, displaying all users and their corresponding orders, even if they have no orders.

7. Construct a database trigger that automatically updates the `last_modified` timestamp column in a table named `Products` whenever a row is updated.

8. Write a query to aggregate sales data, returning the total sales amount for each product in the `Sales` table, sorted by the highest sales first.

9. Create a SQL view named `ActiveUsers` that shows the user ID, username, and last_login date for users who have logged in within the past 7 days.

10. Design an in-memory data structure to efficiently handle real-time searching of user sessions, allowing retrieval of sessions by user ID in constant time.