我在这里只是引入了一个level列，这个列的初值为1，每次加1。

All I have done here is to introduce a level column, which starts with 1 and increments by 1.

youdao

我在这里只是引入了一个level列，这个列的初值为1，每次加1。

All I have done here is to introduce a level column, which starts with 1 and increments by 1.

youdao