View updating and relational theory v413hav
From the standpoint of anthropology and sociology, dating is linked with other institutions such as marriage and the family which have also been changing rapidly and which have been subject to many forces, including advances in technology and medicine.Historically, marriages in most societies were arranged by parents and older relatives with the goal not being love but legacy and "economic stability and political alliances", according to anthropologists. That means they should be updatable, just as "real" or base tables are.In fact, view updatability isn’t just desirable, it’s crucial, for practical reasons as well as theoretical ones.
Ever since the relational model first appeared, there has been widespread skepticism as to whether (in gen Views are virtual tables.
The proposed scheme is 100% consistent with the relational model, but rather different from the way updating works in SQL products today.
This book can: Help database products improve in the future Help with a "roll your own" implementation, absent such product improvements Make you aware of the crucial role of predicates and constraints Show you how relational products are really supposed to behave Anyone with a professional interest in the relational model, relational technology, or database systems in general can benefit from this book.
In this chapter and the next two, I turn my attention to intersection, union, and difference views.
Of course, I’ve already said something in Chapter 6 about intersection views in particular (the subject of the present chapter)—recall that intersection is a special case of one to one join—but there’s quite a lot more to be said on the subject.