数据库已经变得更强大了，所以这个类型层次结构也变得更复杂。

As databases have become more powerful, this type hierarchy has grown more complex.

youdao

数据库已经变得更强大了，所以这个类型层次结构也变得更复杂。

As databases have become more powerful, this type hierarchy has grown more complex.

youdao