INSERT INTO metter_data (NUMBER, obis, DATE, VALUE)
SELECT 
	s.number, 
	s.obis, 
	s.date_from, 
	convert (s.value_from, unsigned) AS value
FROM skaititaji s
UNION
SELECT 
	s.number, 
	s.obis, 
	s.date_to, 
	convert (s.value_to, unsigned) AS value
FROM skaititaji s