Ej3-get_pop_variation_rate.sql

create
or replace
function get_pop_variation_rate( idpais integer ) returns double precision as $$

select
	(c1.poblacion / c1.anio)::float / (c2.poblacion / c2.anio)::float
from
	censos c1,
	censos c2
where
	c1.idPais = $1
	and c2.idPais = $1
	and c1.anio > c2.anio
order by
	c1.anio desc,
	c2.anio desc 
fetch first 1 rows only 

$$ language sql;