PostgreSQL: sobrecarga de funciones

get_rental_duration() a

CREATE OR REPLACE FUNCTION get_rental_duration(p_customer_id INTEGER)
    RETURNS INTEGER AS $$
    
DECLARE 
    rental_duration INTEGER; 
BEGIN
    -- get the rate based on film_id
    SELECT INTO rental_duration SUM( EXTRACT( DAY FROM return_date - rental_date)) 
    FROM rental 
    WHERE customer_id=p_customer_id;

    RETURN rental_duration;
END; $$
LANGUAGE plpgsql;

get_rental_function p_customer_id 278 get_rental_duration

SELECT get_rental_duration(278);

Devuelve lo siguiente:

p_from_date get_rental_duration()

CREATE OR REPLACE FUNCTION get_rental_duration(p_customer_id INTEGER, p_from_date DATE)
    RETURNS INTEGER AS $$
DECLARE 
    rental_duration integer;
BEGIN
    -- get the rental duration based on customer_id and rental date
    SELECT INTO rental_duration
                SUM( EXTRACT( DAY FROM return_date + '12:00:00' - rental_date)) 
    FROM rental 
    WHERE customer_id= p_customer_id AND 
          rental_date >= p_from_date;
     
    RETURN rental_duration;
END; $$
LANGUAGE plpgsql;

get_rental_duration(entero, fecha) 2781 de julio de 2005

SELECT get_rental_duration(278, '2005-07-01');

Dará como resultado lo siguiente: