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DataBind Controls to HBase Data in Delphi


DataBind to HBase data in Delphi with standard data access components and controls.

The CData ODBC driver for HBase supports the ODBC standard to enable integration of live HBase data with visual form designers and other rapid development tools in Delphi. The ODBC driver simplifies data access strategies for applications that share a single codebase like Delphi by providing a single API for database development. This article shows how to how to connect to HBase data and query data from a simple visual component library (VCL) application, as well as from Delphi code.

Create a Connection to HBase 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 Port and Server to connect to Apache HBase.

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

Create VCL Applications with Connectivity to HBase Data

Follow the procedure below to start executing queries to HBase 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 HBase 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 SUM(CustomerName), Price FROM Customers GROUP BY Price
    • 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 HBase with FireDAC Components

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

Connect to HBase 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 := 'myhbase'; FDConnection1.Connected := true;

Create Parameterized Queries

Parameterized resources can improve performance: 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.Open('select * from Customers where ShipCity = :ShipCity',['New York']);

To execute a query that does not return a result set, such as a delete, 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, use the TFD.RowsAffected property.

FDQuery1.ExecSQL('delete from Customers where Id= :myId',['x12345']); i := FDQuery1.RowsAffected;

Related Articles

Below you can find other articles for using the CData ODBC Driver with RAD Studio, Delphi, and C++ Builder.

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The HBase ODBC Driver is a powerful tool that allows you to connect with Apache HBase columnar databases, directly from any applications that support ODBC connectivity.

Access HBase like you would a relational database - read, write, and update through a standard ODBC Driver interface.

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