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SELECT
    user_id,
    charging_station_id,
    charging_cost,
    
    -- Based on the charging_start_time, find the first 
    -- charging cost for each location
	___(___) OVER(
    	PARTITION BY charging_station_id
      	ORDER BY ___
    ) AS first_charging_cost,

	-- Find the average charging cost for charging station id
    ___(___) ___(
        ___ ___ ___
    ) AS average_charging_cost
    
FROM ELECTRIC_VEHICLES.charging
ORDER BY charging_station_id;