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.The README document is installed in the mainDelphi directory.No-nonsense license agreementThe Delphi no-nonsense license agreement, a printed document, covers other legalrights and obligations concerning Delphi.Third-party product documentationRedistribution rights for third-party components, utilities, helper applications,database engines, and other products are governed by the vendor supplying theproduct.Consult the documentation for the product or the vendor for informationregarding the redistribution of the product with Delphi applications prior todistribution.18-16 Dev el oper  s Gui deP a r tIIPart IIDeveloping database applicationsThe chapters in  Developing Database Applications present concepts and skillsnecessary for creating Delphi database applications.Database components are notavailable in all editions of Delphi.Devel opi ng dat abase appl i c at i onsCh a p t e r19Chapter19Designing database applicationsDatabase applications let users interact with information that is stored in databases.Databases provide structure for the information, and allow it to be shared amongdifferent applications.Delphi provides support for relational database applications.Relational databasesorganize information into tables, which contain rows (records) and columns (fields).These tables can be manipulated by simple operations known as the relationalcalculus.When designing a database application, you must understand how the data isstructured.Based on that structure, you can then design a user interface to displaydata to the user and allow the user to enter new information or modify existing data.This chapter introduces some common considerations for designing a databaseapplication and the decisions involved in designing a user interface.Using databasesDelphi includes many components for accessing databases and representing theinformation they contain.They are grouped according to the data access mechanism:" The BDE page of the Component palette contains components that use the BorlandDatabase Engine (BDE).The BDE defines a large API for interacting withdatabases.Of all the data access mechanisms, the BDE supports the broadest rangeof functions and comes with the most supporting utilities.It is the best way towork with data in Paradox or dBASE tables.However, it is also the mostcomplicated mechanism to deploy.For more information about using the BDEcomponents, see Chapter 26,  Using the Borland Database Engine." The ADO page of the Component palette contains components that use ActiveXData Objects (ADO) to access database information through OLEDB.ADO is aMicrosoft Standard.There is a broad range of ADO drivers available forconnecting to different database servers.Using ADO-based components lets youDes i gni ng dat abas e appl i c at i ons 19-1Us i n g d a t a b a s e sintegrate your application into an ADO-based environment (for example, makinguse of ADO-based application servers).For more information about using theADO components, see Chapter 27,  Working with ADO components." The dbExpress page of the Component palette contains components that usedbExpress to access database information.dbExpress is a lightweight set of driversthat provide the fastest access to database information.In addition, dbExpresscomponents support cross-platform development because they are also availableon Linux.However, dbExpress database components also support the narrowestrange of data manipulation functions.For more information about using thedbExpress components, see Chapter 28,  Using unidirectional datasets." The InterBase page of the Component palette contains components that accessInterBase databases directly, without going through a separate engine layer." The Data Access page of the Component palette contains components that can beused with any data access mechanism.This page includes TClientDataset, whichcan work with data stored on disk or, using the TDataSetProvider component alsoon this page, with components from one of the other groups.For more informationabout using client datasets, see Chapter 29,  Using client datasets. For moreinformation about TDataSetProvider, see Chapter 30,  Using providercomponents [ Pobierz całość w formacie PDF ]