Location and existence: 在, 是, 有

在 (zài) for where a thing is, 有 (yǒu) for what is there

Subject + 在 (zài) + place answers 'where is X?': 书在桌子上 (shū zài zhuō zi shàng). Place + 有 (yǒu) + thing answers 'what is at X?': 桌子上有一本书 (zhuō zi shàng yǒu yì běn shū), and whatever follows 有 (yǒu) is always indefinite. Swap them and you get 桌子上有那本书 (zhuō zi shàng yǒu nà běn shū), which does not work for 'that book is on the table'.