SQL Count Customers where Products are the same

I have a problem. I have a SQL-database named customers with the 3 columns Country, CustomerID and Product. With that database, I want to count all the customers which bought the products bike, flask and helmet but grouped by the country as you can see in the following picture.

Is there a chance you can help me out with that? I guess I have to make a join on the same table and make a nested query with another select, but I don’t really know how to do that.

I would be very thankful for your help!

Answer

You have to do aggregation in two steps. First find the customers with the 3 different products, then count these customers.

SELECT country, count(*)
FROM
(
  SELECT country, CustomerID 
  FROM customers 
  WHERE product IN ('Bike','Flask','Helmet') 
  GROUP BY country, CustomerID
  HAVING COUNT(distinct product) = 3
) dt
GROUP BY country