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DataBind Controls to Btrieve Data in C++Builder

DataBind to Btrieve data in C++ Builder with standard components and controls.

The CData ODBC Driver for Btrieve makes it easy to integrate connectivity to live Btrieve data with standard data access components in C++Builder. This article shows how to create a simple visual component library (VCL) application in C++Builder that connects to Btrieve data, executes queries, and displays the results in a grid. An additional section shows how to use FireDAC components to execute commands from code.

Create a FireDAC Connection to Btrieve Data

Follow the steps below to use the Data Explorer to create a FireDAC connection to Btrieve.

  1. If you have not already, specify connection properties in a DSN (data source name). You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

    Below is a typical connection string:

    User=myuser;Password=mypassword;Server=myserver;Database=mydatabase;

    See the "Getting Started" chapter in the help documentation for a guide to setting the required properties in the Microsoft ODBC Data Source Administrator.

  2. In a new VCL Forms application, expand the FireDAC node in the Data Explorer.
  3. Right-click the ODBC Data Source node in the Data Explorer.
  4. Click Add New Connection.
  5. Enter a name for the connection.
  6. In the FireDAC Connection Editor that appears, set the DataSource property to the name of the ODBC DSN for Btrieve.

Create VCL Applications with Connectivity to Btrieve Data

Follow the procedure below to start querying Btrieve data from a simple VCL application that displays the results of a query in a grid.

  1. Drop a TFDConnection component onto the form and set the following properties:

    • ConnectionDefName: Select the FireDAC connection to Btrieve.
    • Connected: Select True from the menu and, in the dialog that appears, enter your credentials.
  2. Drop a TFDQuery component onto the form and set the properties below:

    • Connection: Set this property to the TFDConnection component, if this component is not already specified.
    • SQL: Click the button in the SQL property and enter a query. For example:

      SELECT * FROM Billing
    • Active: Set this property to true.
  3. Drop a TDataSource component onto the form and set the following property:

    • DataSet: In the menu for this property, select the name of the TFDQuery component.
  4. Drop a TDBGrid control onto the form and set the following property:

    • DataSource: Select the name of the TDataSource.
  5. Drop a TFDGUIxWaitCursor onto the form — this is required to avoid a run-time error.

Execute Commands to Btrieve with FireDAC Components

You can use the TFDConnection and TFQuery components to execute queries to Btrieve data. This section provides Btrieve-specific examples of executing queries with the TFQuery component.

Connect to Btrieve Data

To connect to the data source, set the Connected property of the TFDConnection component to true. You can set the same properties from code:

FDConnection1->ConnectionDefName = "CData Btrieve ODBC Source"; FDConnection1->Connected = true;

To connect the TFDQuery component to Btrieve data, set the Connection property of the component. When a TFDQuery component is added at design time, its Connection property is automatically set to point to a TFDConnection on the form, as in the application above.

Create Parameterized Queries

To create a parameterized query, use the following syntax below:

FDQuery1->SQL->Text = "select * from Billing where student_id = :Student_ID"; FDQuery1->ParamByName("student_id")->AsString = "22"; query->Open();

The example above binds a string-type input parameter by name and then opens the dataset that results.

Prepare the Statement

Preparing statements is costly in system resources and time. The connection must be active and open while a statement is prepared. By default, FireDAC prepares the query to avoid recompiling the same query over and over. To disable statement preparation, set ResourceOptions.DirectExecute to True; for example, when you need to execute a query only once.

Execute a Query

To execute a query that returns a result set, such as a select query, use the Open method. The Open method executes the query, returns the result set, and opens it. The Open method will return an error if the query does not produce a result set.

FDQuery1->SQL->Text := "select * from Billing where student_id = :Student_ID"; FDQuery1.ParamByName("student_id")->AsString = "22"; FDQuery1->Open();

To execute a query that does not return a result set, use the ExecSQL method. The ExecSQL method will return an error if the query returns a result set. To retrieve the count of affected rows for an insert, update, or delete, use the TFD.RowsAffected property.

FDQ.SQL.Text := "delete from Billing where Id = :Id"; FDQuery1->Params->Items[0]->AsString = "x12345"; FDQuery1->ExecSQL(); AnsiString i = FDQuery1->RowsAffected;
 
 
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