SQL Challenges

Retrieve all products from the products table. This is a basic SELECT query to get familiar with querying data.

Count the total number of employees in the company.

Find all products that cost less than $100.

Retrieve customer information for customers whose email ends with '@gmail.com'.

Calculate the average salary for each department.

Report the students who scored 90 or above in the most recent algorithm exam. Provide their identifiers, names, and scores ranked from highest to lowest.

Find customers who have placed more than 2 orders and show their total spending.

Calculate total revenue for each product category and show only categories with revenue over $500.

List all employees along with their manager's name. Show employees who have a manager.

Calculate total sales for each month in 2024 and show the month name and total.

Find users who have logged in for at least 3 consecutive days and show their longest streak.

Find the second highest salary in each department. If a department has only one employee, return NULL.

Calculate the month-over-month retention rate: the percentage of customers who made purchases in both the current and previous month.

Find pairs of products that are frequently bought together (in the same order). Show pairs that appear in at least 2 orders.

Calculate a running total of daily sales for each product category, but reset the total when it exceeds $1000.