There are several significant details that I would like to tell you in advance中的that I would like to tell you in advance
是定語從句，引導詞that作tell的直接賓語，tell sb sth。定語從句的引導詞在定語從句中充當一定的成分（作主語、賓語、定語、狀語），而同位語從句的引導詞在從句中不充當成分，其前面的詞往往是idea/opinion/suggestion/advice/ view/news等，同位語從句所表示的是觀點、建議、新聞的具體內容，從句與前面的idea等是同位關係，不存在修飾與被修飾、限制與被限制的關係。再看
Do you agree with the idea that/which I came up with yesterday?（定語從句）
Do you agree with the idea that we should finish the work in two days?（同位語從句）
There are several significant details that I would like to tell you in advance中的that I would like to tell you in advance
是定語從句，引導詞that作tell的直接賓語，tell sb sth。定語從句的引導詞在定語從句中充當一定的成分（作主語、賓語、定語、狀語），而同位語從句的引導詞在從句中不充當成分，其前面的詞往往是idea/opinion/suggestion/advice/ view/news等，同位語從句所表示的是觀點、建議、新聞的具體內容，從句與前面的idea等是同位關係，不存在修飾與被修飾、限制與被限制的關係。再看
Do you agree with the idea that/which I came up with yesterday?（定語從句）
Do you agree with the idea that we should finish the work in two days?（同位語從句）