-- Write a SQL query to count the number of unique users per day who logged in from both iPhone and web,
-- Where iPhone logs and web logs [log-ins] are in distinct relations.
-- originally taken from:
-- https://www.youtube.com/watch?v=Td-cmLfQ7uU&list=PLVD3APpfd1tuXrXBWAntLx4tNaONro5dA