DELIMITER //

CREATE OR REPLACE FUNCTION getDaysBetween(starting_date DATETIME, ser_num VARCHAR(25))
RETURNS INT
NOT DETERMINISTIC

BEGIN

	DECLARE fiscal_year VARCHAR(4);
    DECLARE actual_year_begin VARCHAR(25);
    DECLARE first_yearly_meter_read_date VARCHAR(25);
    DECLARE total_printing_days INT;
	
	 
    
    /*Declare the cursor that will get the earliest meter read date for this serial number that is
    	in the same fiscal year as the starting_date. The total days, used to CALCULATE THE AVERAGE
        copies/day, will be the difference between the first actual meter read for this
        serial number and the starting_date. 1 row will be returned.*/
        
    DECLARE getFirstMeterReadDate CURSOR FOR
    
    SELECT MIN(created_date) first_meter_read_date    
    FROM y2019_meters
    WHERE serial_number = ser_num
    AND created_date BETWEEN actual_year_begin AND starting_date
    GROUP BY serial_number;   
    
    
    
    /*Concat the date that the fiscal year begins. Use the same year
    	as the starting_date and the default fiscal date .*/
	SELECT YEAR(starting_date) INTO fiscal_year;

	SET actual_year_begin = CONCAT(fiscal_year, '-07-01 00:00:00');

	OPEN getFirstMeterReadDate;
     
		FETCH getFirstMeterReadDate INTO first_yearly_meter_read_date;

	CLOSE getFirstMeterReadDate;
    
    
    /*Get total_printing_days. This will be divided into the total copies for the
		same time period, to get the average copies printed per day.*/
	SELECT DATEDIFF(starting_date, first_yearly_meter_read_date) INTO total_printing_days;
	 
     
	RETURN total_printing_days;

END //

DELIMITER ;