Ficha 11 ex2

CREATE OR REPLACE FUNCTION sumary_temp() returns TRIGGER
language plpgsql
AS $$
BEGIN
    DELETE FROM temp;
    INSERT INTO temp (col1, col2, message)
        (SELECT  SUM(preco), COUNT(*), genero
           FROM livros
          GROUP BY genero);

    RETURN NULL; -- se for chamado num trigger de statemetn vai dar null na mesma
END;
$$;


CREATE TRIGGER actualiza_temp
 after INSERT OR DELETE OR UPDATE OF genero, preco ON livros
 -- nao faz sentido -- for each row
EXECUTE PROCEDURE sumary_temp();