2.8 DATABASE COMPONENTS IN SOME POPULAR DATABASES
All databases allow for storage, retrieval and management of the data. Simple databases provide basic services to accomplish these tasks. Many database providers, like Microsoft SQL Server and Oracle, provide additional services that necessitate storing many components in the database other than data. These components, such as views, stored procedures and so on, are collectively called database objects. In this section, we will discuss various objects that make up MS Access, SQL Server and Oracle databases.
There are two major types of databases, file server and client server.
In a file server database, data is stored in a file, and each user of the database retrieves the data, displays the data or modifies the data directly from or to the file. In a client server database, the data is also stored in a file; however, all these operations are mediated through a master program called a server. MS Access is a file server database, whereas Microsoft SQL Server and Oracle are client server databases. Client server databases have several advantages over file server databases. These include minimizing the chance of crashes, provision of features for recovery, enforcement of security, better performance and more efficient use of the network compared to file server databases.
2.8.1 Microsoft Access Databases
The Microsoft Access Database Engine is a collection of information stored in a systematic way that forms the underlying component of a database. Also called Jet (Joint Engine Technology), it allows the manipulation of a relational database. It offers a single interface that other software may use to access Microsoft databases. The supporting software is developed to provide security, integrity, indexing, record locking and so on. By executing the MS Access program, MSACCESS.EXE, you can see the database engine at work and the user interface it provides. Figure 2.9 shows how a Java application accesses the MS Access database via the ACE OLE database provider.
2.8.1.1 Database File
An Access database is made up of a number of components called objects, which are stored in a single file referred to as database file. As new objects are created or more data is added to the database, this file gets bigger. This is a complex file that stores objects like Tables, queries, forms, reports, macros and modules. Access files have an. mdb (Microsoft DataBase) extension. Some of these objects help the user work with the database; others are useful for displaying database infor-mation in a comprehensible and easy-to-read format.
FIGURE 2.9 Microsoft Access database illustration.