CREATE or replace FUNCTION somefunc() RETURNS integer AS $$
DECLARE
   quantity integer := 30;
BEGIN
   RAISE NOTICE 'Quantity here is %', quantity;  -- 在这里的数量是 30
   quantity := 50;
   --
   -- 创建一个子块
   --
   DECLARE
      quantity integer := 80;
   BEGIN
      RAISE NOTICE 'Quantity here is %', quantity;  -- 在这里的数量是 80
   END;
   RAISE NOTICE 'Quantity here is %', quantity;  -- 在这里的数量是 50
   RETURN quantity;
END;
$$ LANGUAGE plpgsql;

select somefunc() as i;