Databases Reference
In-Depth Information
10
DBMS
Database
User
FIGURE 1-8
Using a DBMS directly
In other cases, users may interact with programs such as those created with Visual Basic, Java, Perl, PHP,
or C++; these programs, in turn, interact with the DBMS, as shown in Figure 1-9. In either case, only the DBMS
actually accesses the database.
Program
DBMS
Database
User
FIGURE 1-9
Using a DBMS through another program
With a DBMS, for example, users at Premiere Products can ask the system to find data about part KV29;
the system will either locate the part and provide the data or display a message that no such part exists in the
database. All the work involved in this task is performed by the DBMS. If part KV29 is in the database, users then
can ask for the order lines that contain the part; and again the system will perform all the work involved in
locating the order lines. Likewise, when users add data about a new customer to the database, the DBMS per-
forms all the tasks necessary to ensure that the customer data is added and that the customer is related to the
appropriate rep.
Popular DBMSs include Access, Oracle, DB2, MySQL, and SQL Server. Because Premiere Products uses
the Microsoft Office suite of programs, which includes Access, management elects to use Access as its DBMS
initially. Using the tables shown in Figure 1-5 as the starting point, a database expert at Premiere Products
determines the structure of the required database—this process is called
database design
. Then this person
enters the design in the DBMS and creates several
forms
, which are screen objects used to maintain, view,
and print data from a database. Employees then begin to enter data.
The form that employees use to process part data is shown in Figure 1-10. Using this form, employees can
enter a new part; view, change, or delete an existing part; and print the information for a part. No one at Pre-
miere Products needs to write a program to create this form; instead, the DBMS creates the form based on
answers provided in response to the DBMS's questions about the form's content and appearance.
