Database Reference
In-Depth Information
•
A front-end system (such as Delphi, C++ Builder, Visual Basic, etc.)
is being used to construct a user interface for a software system
that accesses one or more underlying databases. The software
developer incorporates embedded SQL statements in various
application queries, based on user input. This request is then sent
to the relevant database server to be serviced. The database server
processes the request and sends the response back to the client.
•
A database administrator needs to periodically back up several
components of an Oracle database. Rather than repeatedly
issuing backup statements for the different items (for instances
tablespaces) he/she may write an SQL script to dynamically
generate the required SQL statements needed to perform backup
of each component.
Figure
12-15
illustrates an inquiry screen for an application developed in Delphi.
The end user is accessing a database for a list of publishers that the institution conducts
business with. On the screen, you will notice a push button labeled
Search
, a radio group
(with entries
ByCode
and
ByName
), and an input field. This application program works
as follows:
•
The end user can specify any search argument in the input field,
to indicate the starting publisher code or name of interest (blank
means start at the beginning of the list of publishers).
•
The user will use the radio group to select whether information
will be displayed sorted by publisher code or publisher name.
•
When the user clicks the
Search
push button, the program will
examine the entries made, build an appropriate SQL statement to
fetch the information requested, invoke the SQL parser to request
this information from the underlying database (which could be in
a different back-end system such as Oracle, DB2, etc.). The code
for building the SQL statement is shown in the figure.
•
The database server that receives this request will process it and
return the information to the program. The program will then
load the grid shown with the information, display it on screen,
and then await the next request from the end user.
