Access Database Design and Programming, Second Edition

Chapter 14. Programming DAO: Overview

We have seen that Access SQL provides a way to create and manipulate database objects, such as tables and queries, through its DDL and DML components. In addition, users can enter SQL statements directly into the Access SQL View window.

On the other hand, Microsoft Access allows us to program the Jet database engine directly, through its programming interface, which is known as Data Access Objects , or DAO. This gives the user far more control over a database.

DAO is a complicated structure, and we will not discuss all of its aspects. Our focus in this book will be on gaining a general understanding of the following concepts and components:

• The organization of DAO, which is at least partly object-oriented

• The DDL component of DAO

• The DML component of DAO

We will certainly not cover all aspects of the DDL and DML components. Our main goal is to prepare you so that you can get whatever additional information you need from Microsoft Access’s extensive on-line help for the DAO model, or from similar hardcopy reference manuals.

Objects

Before discussing the various components of the DAO model, we must discuss the concept of an object . In the parlance of object-orientation, an object is something that is identified by its properties and its methods (or actions).

As we will see (and as the name implies) DAO is full of objects. For example, each saved table in an Access database is an object, called a TableDef object. (Actually, it is the definition of the ...