drop table if exists rates;	
create table rates(origin varchar, dest varchar, distance int, "r2023" decimal(38,10), "r2022" decimal(38,10), "r2021" decimal(38,10));
insert into rates values ('a', 'b', 500, 2023.12, 2022.23, 2021.34);
insert into rates values ('a', 'c', 500, 2023.11, null, null);
-- futher nulls
insert into rates values ('a', 'd', 400, null, null, null);
insert into rates values ('a', 'e', null, null, null, null);

WITH source AS(
	SELECT origin, 
		dest,  
		distance, 
		"r2023", 
		"r2022",
		"r2021"
	FROM "rates"
)
SELECT r.origin, r.dest, r.rates, r.values
FROM (
	SELECT source.origin, 
		source.dest, 
		v.rates,
		v.values
	FROM source 
	JOIN LATERAL (
		VALUES 
			(source."distance", 'distance'), 
			(source."r2023", 'r2023'), 
			(source."r2022", 'r2022'),  
			(source."r2021", 'r2021')
	) AS v ("values", "rates") ON true
) AS r