Duy trì hiệu suất bộ sạc

SELECT
    user_id,
    charging_station_location,
    charging_start_time,
    charging_rate,
	
    -- Difference between current charging rate versus three sessions ago
    ___ - ___(___, ___, 0) OVER(
      	
      	-- Make sure results are partitioned by charging_station_location
        ___
      
      	-- Sessions should be ordered by when charging began
        ___
      
    ) AS change_in_charging_rate

FROM ELECTRIC_VEHICLES.charging;