Non computer major, this two days in the database design, relevant knowledge, including the database physical structure design in the link, a part of the data access method, but the Internet down still don't quite understand, what I see main method b tree, b + tree, hash this category, and clustering index, the clustering index this category, but without the introduction of a unified, excuse me these two types of data access method is a parallel relationship (two different classification method) or containment relationship (such as b tree clustering index and the clustering index)? What are the advantages and disadvantages? Or have good posts can also share online, thank you!