Ranking gym members by efficiency

SELECT
    user_id,
    gym_id,
    checkin_time,

	-- Determine workout efficiency for each user using the check in/out
    -- time, as well as the number of calories burned
    ___(
        ___, 
        ___, 
        ___
    ) AS ___  -- Alias the results as workout_efficiency

FROM CORE_GYM.visits

-- Order the results by workout_efficiency
___ ___ ___ DESC;