SELECT @first_date := MIN(created_date) first_date, @last_date := MAX(created_date) last_date, serial_number,
DATEDIFF('2018-12-18 13:18:06', '2018-07-01 00:00:00') tot_days
FROM y2019_meters
WHERE serial_number = '2030004'
AND created_date BETWEEN '2018-12-18 13:18:06' AND '2019-06-30 23:59:59'
GROUP BY serial_number;



SELECT *
FROM y2019_meters
WHERE serial_number = '2030004'
AND created_date BETWEEN '2018-12-18 13:18:06' AND '2019-06-30 23:59:59'
ORDER BY created_date;




SELECT MIN(created_date) first_date, MAX(created_date) last_date, serial_number,
DATEDIFF('2018-12-18 13:18:06', '2018-09-25 12:17:08') tot_days
FROM y2019_meters
WHERE serial_number = '2030004'
AND created_date BETWEEN '2018-12-18 13:18:06' AND '2019-06-30 23:59:59'
GROUP BY serial_number;

SELECT MIN(created_date) first_meter_read_date, serial_number    
    FROM y2019_meters
    WHERE serial_number = '2030004'
    AND created_date BETWEEN '2018-07-01 00:00:00' AND '2018-12-18 13:18:06'
    GROUP BY serial_number; 
    
SELECT * FROM y2019_meters
    WHERE serial_number = '2030004'
    ORDER BY created_date;