Contents Should we tell you the whole story? Of course, there is an inevitable tension in trying to work like this. For example, in Chapter 16 we talk about referential integrity. There are - sentially six different flavors of referential integrity but Access only s- ports four of them (they are the most important ones however, so you aren?t missing out on too much). The problem is this. Should we tell you about the other two? If we do, as an Access user you have every right to be annoyed that we are telling you about a feature you can?t use. On the other hand, the six different types that we describe are part of the re- tional world and this book is about that world ? we are not trying to teach you how to use Access, we are simply using Access to illustrate the relational model. Ultimately we decided to risk your ire and to describe all of the features of the relational model as we see it, even if Access doesn?t support all of them. One advantage of this approach is that if you need to use a different database engine you will almost certainly find the extra information useful. Incidentally, this is not meant to imply that Access is somehow lacking as a relational database engine. The reason we chose it for the first book is that it is such a good example of a relational database tool.