The following procedure describes how to build a dbExpress database application.
Building a VCL Forms dbExpress application consists of the following major steps:
- Set up the database connection.
- Set up the unidirectional dataset.
- Set up the data provider, client dataset, and data source.
- Connect a DataGrid to the connection components.
- Run the application.
To add a dbExpress connection component
- Choose FileNewOtherDelphi Projects or C++Builder Projects and double-click the VCL Forms Application icon. The VCL Forms Designer is displayed.
- From the dbExpress page of the Tool Palette, place a TSQLConnection component on the form.
- Double-click the TSQLConnection component to display the Connection Editor.
- In the Connection Editor, set the Connection Name field to IBConnection.
- In the Connections Setting box, specify the path to the InterBase database file called employee.gdb in the Database field. By default, the file is located in C:\Program Files\Common Files\Borland Shared\Data.
- Accept the value in the User_Name field (sysdba) and Password field (masterkey).
- Click OK to close the Connection Editor and save your changes.
To set up the unidirectional dataset
- In the Tool Palette on the dbExpress page, place a TSQLDataSet component at the top of the form.
- In the Object Inspector, select the SQLConnection property drop-down list. Set it to TSQLConnection1.
- Set the CommandText property to an SQL command, for example, Select * from SALES. You are prompted to log in. Use the masterkey password. For the SQL command, you can either type a Select statement in the Object Inspector or click the ellipsis to the right of CommandText to display the CommandText Editor where you can build your own query statement.
Tip: If you need additional help while using the CommandText Editor
, click the Help button.
- In the Object Inspector, set the Active property to True to open the dataset.
To add the provider
- In the Tool Palette on the Data Access page, place a TDataSetProvider component at the top of the form.
- In the Object Inspector, select the DataSet property drop-down list. Set it to SQLDataSet1.
To add client dataset
- In the Tool Palette on the Data Access page, place a TClientDataSet component to the right of the TDataSetProvider component on the form.
- In the Object Inspector, select the ProviderName drop-down. Set it to DataSetProvider1.
- Set the Active property to True to allow data to be passed to your application. A data source connects the client dataset with data-aware controls. Each data-aware control must be associated with a data source component to have data to display and manipulate. Similarly, all datasets must be associated with a data source component for their data to be displayed and manipulated in data-aware controls on the form.
To add the data source
- In the Tool Palette on the Data Access page, place a TDataSource component to the right of the TClientDataSet on the form.
- In the Object Inspector, select the DataSet property drop-down. Set it to ClientDataSet1.
To connect a DataGrid to the DataSet
- In the Tool Palette on the Data Controls page, place a TDBGrid component on the form.
- In the Object Inspector, select the DataSource property drop-down. Set the data source to DataSource1.
- ChooseRunRun. You are prompted to enter a password. Enter masterkey. If you enter an incorrect password or no password, the debugger throws an exception. The application compiles and displays a VCL form with a DBGrid.