#SELECT * FROM `Y2017_meter` WHERE serial_number LIKE('C%')
SELECT * FROM `Y2015_meter` WHERE serial_number LIKE('U%') #1163665
#DELETE FROM `Y2015_meter` WHERE serial_number LIKE('U%') 
#DROP TABLE `Y2013_meter`;

#ALTER TABLE `Y2018_meter_2` ADD INDEX idx_serNum (serial_number);
#ALTER TABLE `Y2017_meter_2` ADD INDEX idx_serNum (serial_number);
#ALTER TABLE `Y2016_meter_2` ADD INDEX idx_serNum (serial_number);
ALTER TABLE `Y2015_meter_2` ADD INDEX idx_serNum (serial_number);

serial_number = p-kitchen #72 rows
serial_number = UUUUUUUUUUUUUU
serial_number = ''
serial_nimber = NULL