PostgreSQL - Función para encontrar la mayor diferencia entre fechas

CREATE OR ALTER PROCEDURE DIAS_SIN RETURNS (

	"RESULT" INTEGER

)

AS

DECLARE VARIABLE AUX INTEGER;

BEGIN

  AUX    = 0;

  RESULT = 0;

  FOR

    SELECT max(DATEDIFF(DAY FROM DT2.FECHA TO DT1.FECHA))

  FROM DATOS DT1, DATOS DT2

  WHERE DT1.SALIDA_NUM = DT2.SALIDA_NUM + 1

    INTO :AUX

  DO

    IF(AUX > RESULT) THEN RESULT = AUX;

  SUSPEND;

END

CREATE OR REPLACE FUNCTION public.dias_sin()RETURNS BIGINT LANGUAGE 'plpgsql'

AS

$$

DECLARE

 MAX_DIF BIGINT;

BEGIN

      SELECT max(DT2.FECHA - DT1.FECHA) INTO  MAX_DIF

      FROM DATOS DT1, DATOS DT2  WHERE DT1.SALIDA_NUM = DT2.SALIDA_NUM + 1;

     RETURN COALESCE(MAX_DIF,0);

END;

$$

CREATE OR REPLACE FUNCTION public.dias_sin()RETURNS BIGINT LANGUAGE 'plpgsql'

AS

$$

DECLARE

 MAX_DIF BIGINT;

BEGIN

      SELECT max(DT2.FECHA::DATE - DT1.FECHA::DATE) INTO  MAX_DIF

      FROM DATOS DT1, DATOS DT2  WHERE DT1.SALIDA_NUM = DT2.SALIDA_NUM + 1;

     RETURN COALESCE(MAX_DIF,0);

END;

$$