Building a VCL Forms dbExpress Database Application
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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 either File > New > VCL Forms Application - Delphi or File > New > VCL Forms Application - C++Builder .
- From the dbExpress page of the Tool Palette, place a TSQLConnection component on the form.
- Click the TSQLConnection component from the form and set its ConnectionName property to IBConnection, in the Object Inspector. This setting automatically does the following:
- Sets the Driver property to INTERBASE.
- Assigns a UserName (sysdba) and a PassWord (masterkey) to provide secured access to the database.
- You need to specify the path to your InterBase database file (your .gdb file) in the Database field.
To set up the unidirectional dataset:
- In the Tool Palette on the dbExpress page, place a TSQLDataSet component on the form.
- In the Object Inspector, select the SQLConnection property drop-down list. Set it to the name of your TSQLConnection component.
- Set the CommandText property to an SQL command, for example, Select * from Table_Name. 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 at 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 on the form.
- In the Object Inspector, select the DataSet property drop-down list. Set it to the name of your TSQLConnection component.
To add client dataset:
- In the Tool Palette on the Data Access page, place a TClientDataSet component on the form.
- In the Object Inspector, select the ProviderName drop-down. Set it to the name of your TDataSetProvider component.
- 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 on the form.
- In the Object Inspector, select the DataSet property drop-down. Set it to the name of your TClientDataSet component.
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 the name of your TDataSource component.
- Choose Run > Run . 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.
The connections between the different components follow this diagram: