The Oracle_CQN sample shows you how to use Continuous Query Notification with Oracle databases using FireDAC.
Table of Contents
You can find the Oracle_CQN project at:
- Start | Programs | Embarcadero RAD Studio Sydney | Samples and then navigate to:
Object Pascal\Database\FireDAC\Samples\DBMS Specific\Oracle\CQN
- Subversion Repository:
- You can find Delphi code samples in GitHub Repositories. Search by name into the samples repositories according to your RAD Studio version.
|File in Delphi||Contains|
|The project itself.|
|The main form.|
Before running the sample, the main components are configured at design time using the Object Inspector as follows:
- Two TFDConnection objects named conOriginal and conChanges. These are the FireDAC connection objects that the sample use to connect to a DBMS. The sample sets the ConnectionDefName property of conOriginal to
- You can change the ConnectionDefName property to connect to a different Oracle server using a valid user name and password.
- The Params properties of conChanges are copied from conOriginal on run-time.
- Two TFDQuery objects named qOriginal and qChanges. These component are used to implement datasets capable of executing SQL queries.
- A TFDEventAlerter object named eaChanges. This component is used to handle the database change notifications.
- Three TDataSource objects named dsOriginal, dsChanges and dsRemote. These components provide interfaces between a dataset component and data-aware controls on a form. In this sample, these objects are used to provide communication between the datasets and the grids where the datasets are displayed. To this end, the sample sets the following properties:
- The DataSet property of dsOriginal, dsChanges and dsRemote is set to
- The DataSource property of grdOriginal, grdChanges and grdremote is set to
When you run the application, you see the following components:
- A TButton called Open DB. When you click this button, the sample takes the following steps:
- Connects conOriginal and activates qOriginal.
- Connects conChanges with the same parameters than conOriginal
- Activates the eaChanges event alerter.
- Activates qOriginal.Note: As commented in the Description, you should activate TFDEventAlerter before executing the tracked TFDQuery.
- A TButton called Start TX. When you click this button, the sample starts the transaction.
- A TButton called Commit TX. When you click this button, the sample commits the transaction.
- Three TGrids labeled as: Original data, Change View and “Remote” data. When you modify the data in the first grid, which contains the original data, it triggers a change in the second grid. The changes appear automatically on the second grid due to the event alerter. Moreover, the changes appear highligthed in yellow.
- Two TComboBoxes labeled as Data mode and Refresh mode. You can use these comboboxes to choose between different modes.
- Four TButtons above the third grid. Use these buttons to merge, commit and undo the changes.
- A TCheckBox labeled as Merge using stream. This check box allows you to emulate a remote data transfer.
Fore more information and official connections to other samples, follow the link below: