Write a query to find the count of distinct cities in a table of customers.

Find customers whose first names start with A and come from a particular city.

Create a query to find the most common city for customers.

Write a query to list the customers from a particular country that have not yet placed any orders.

Create a query to find the customers with the most orders in a specified month.

Calculate the total cost for all orders placed by a particular customer.

Create a query to find the average number of orders placed by customers in a particular city.

Write a query to list the customers whose payments have been rejected in the past month.

Create a query to find the total number of orders placed by customers in a particular region.

Write a query to find the average order value from customers who have placed more than three orders.