There be vs. have/有

There be vs. have/有，There be 多用在「存在」，have/has 用在「所有/屬關係」：

There are four trees in the garden.

I have a bicycle.

Additional note:
(1)There are four rooms in the building.
(2)The building has four rooms.
以上兩種說法都是可以的，但(1)重點放在room/房間，(2)重點放在building/建築。