lecture d'un id d'une ligne précise

Bonjour,
Je veux créer une requete qui me retourne la valeur id de la ligne numéro 5 (par exemple) du mon tableau.

Code:

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CREATE OR REPLACE FUNCTION insertnewcountry(nam character varying, country character varying, descr character varying, nbrcurrebcy integer, is_ac character varying, creby character varying, lang character)
  RETURNS void AS
$BODY$ 
DECLARE 
r Integer;
toto Integer := 0;
currencyid Integer:=0;
BEGIN
FOR r IN
   EXECUTE 'SELECT c_currency_id FROM c_currency order by c_currency_id'
   LOOP
      IF toto=nbrcurrebcy THEN
      currencyid=r;
      ELSE toto:=toto+1;
      END IF;
   END LOOP;
 
INSERT INTO c_country (name,countrycode,description,c_currency,is_active,createdby,s_langage)
VALUES (nam,country,descr,currencyid,is_ac,creby,lang) ;            
END;
$BODY$
  LANGUAGE 'plpgsql' VOLATILE
  COST 100;

Merci d'avance,