====== Fonctions utiles pour les dates ======
===== Fonction de vérification de l'existence d'une date =====

<code sql>
CREATE OR REPLACE FUNCTION cenlr_date_est_valide(integer, integer, integer)
  RETURNS boolean AS
$BODY$
DECLARE
	jour alias for $1;
	mois alias for $2;
	annee alias for $3;
	var_result boolean;
   BEGIN
        IF (mois IN (1,3,5,7,8,10,12) AND jour <=31) THEN
            var_result = true;
            RETURN var_result;
        ELSIF (mois IN (4,6,9,11) AND jour <=30) THEN
            var_result = true;
            RETURN var_result;
        ELSIF ((mois = 2 AND (annee % 4) = 0 AND jour <=29) OR (mois = 2 AND (annee % 4) <> 0 AND jour <=28)) THEN
            var_result = true;
            RETURN var_result;
        ELSE var_result = false;
            RETURN var_result;
        END IF;
        RETURN null;
    END;

$BODY$
  LANGUAGE 'plpgsql' VOLATILE
  COST 100;
</code>

===== Fonction de nommage du jour passé en paramètre =====
<code sql>
CREATE OR REPLACE FUNCTION day_name(date)
  RETURNS text AS
$BODY$
DECLARE
	date_test alias for $1;
	var_result text;
	myrec RECORD;
   BEGIN
        FOR myrec IN 
		SELECT CASE extract(isodow from date_test)
WHEN 1 then 'lundi'
WHEN 2 THEN 'mardi'
WHEN 3 THEN 'mercredi'
WHEN 4 THEN 'jeudi'
WHEN 5 THEN 'vendredi'
WHEN 6 THEN 'samedi'
WHEN 7 THEN 'dimanche'
END as jour
	LOOP
		var_result:=myrec.jour;
	END LOOP;
	RETURN var_result;
    END;
$BODY$
  LANGUAGE 'plpgsql' VOLATILE
  COST 100;
</code>
<code sql>
$> select day_name('2010-02-07');
$> dimanche
</code>