It is the same today that it always was语法问题

问题描述:

It is the same today that it always was语法问题
原文是A good book may be among the best of friends.It is the same today that it always was ,and it never change.
请问这里的that是什么用法,是定语从句吗?怎么从语法角度来理解It is the same today that it always was的意思

that 这里是连词,相当于as