Build a Simple VCL Application for Cassandra Data

Embarcadero RAD Studio provides a development environment for Delphi and C++Builder applications. With the CData ODBC Driver for Cassandra, you gain access to live Cassandra data within RAD Studio, abstracting the data into tables, views, and stored procedures that can be used to retrieve and update Cassandra data. This article will walk through connecting to Cassandra and creating a simple VCL application with the Form Designer.

Create a Connection to Cassandra Data

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

Set the Server, Port, and Database connection properties to connect to Cassandra. Additionally, to use internal authentication set the User and Password connection properties.

You can then follow the steps below to use the Data Explorer to create a FireDAC connection to Cassandra data.

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

Create VCL Applications with Connectivity to Cassandra Data

Follow the procedure below to start executing queries to Cassandra 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 Cassandra data.
   • 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 City, SUM(TotalDue) FROM Customer GROUP BY City
   • 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.

You now have an executable application that displays the results of the SQL Query set in the TFDQuery object.