Can you explain about the grammatical structure of "so do I"?

Native speaker’s answer
Rebecca
The structure "so do I" is used to add to the sentence before. It uses the same auxiliary verb as in the previous sentence. We use "so do I" to say that a positive sentence is also true for us. Ex: A: I hate mushrooms. B: So do I (=I also hate mushrooms). Ex: Lucy likes coffee. So do I. Of course, we can also use this expression to talk about what’s true for other people, not just ourselves: Ex: A: I hate mushrooms. B. So does Laura.