Finding how many times a value is shown on a table - Postgresql
Test

SELECT employee.employee_id,
       COUNT(DISTINCT pr.subscription_type) AS types_count
FROM employee
INNER JOIN person p USING(email)
INNER JOIN order o USING(email)
INNER JOIN product pr ON o.product_id = pr.product_id
-- INNER JOIN subscription s ON pr.subscription_type = s.subscription_type
GROUP BY employee.employee_id
ORDER BY employee_id