DataBind Controls to Presto Data in C++Builder

The CData ODBC driver for Presto makes it easy to integrate connectivity to live Presto 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 Presto data, executes queries, and displays the results in a grid. An additional section shows how to use FireDAC components to execute commands from code.

Getting Started

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Create a Connection to Presto 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 and Port connection properties to connect, in addition to any authentication properties that may be required.

To enable TLS/SSL, set UseSSL to true.

Authenticating with LDAP

In order to authenticate with LDAP, set the following connection properties:

• AuthScheme: Set this to LDAP.
• User: The username being authenticated with in LDAP.
• Password: The password associated with the User you are authenticating against LDAP with.

Authenticating with Kerberos

In order to authenticate with KERBEROS, set the following connection properties:

• AuthScheme: Set this to KERBEROS.
• KerberosKDC: The Kerberos Key Distribution Center (KDC) service used to authenticate the user.
• KerberosRealm: The Kerberos Realm used to authenticate the user with.
• KerberosSPN: The Service Principal Name for the Kerberos Domain Controller.
• KerberosKeytabFile: The Keytab file containing your pairs of Kerberos principals and encrypted keys.
• User: The user who is authenticating to Kerberos.
• Password: The password used to authenticate to Kerberos.

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

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 Presto.

Create VCL Applications with Connectivity to Presto Data

Follow the procedure below to start querying Presto 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 Presto.
   • 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 FirstName, LastName FROM Customer WHERE Id = '123456789'
     

   • 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 Presto with FireDAC Components

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

Connect to Presto 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 Presto ODBC Source";
FDConnection1->Connected = true;

To connect the TFDQuery component to Presto 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 Customer where id = :Id";
FDQuery1->ParamByName("id")->AsString = "123456789";
FDQuery1->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 Customer where id = :Id";
FDQuery1->ParamByName("id")->AsString = "123456789";
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 use the TFD.RowsAffected property.

FDQuery1->SQL->Text = "delete from Customer where Id = :Id";
FDQuery1->Params->Items[0]->AsString = "x12345";
FDQuery1->ExecSQL();
AnsiString i = FDQuery1->RowsAffected;
ShowMessage("Rows affected: " + i);

Related Articles

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

• DataBind Controls to Presto Data in Delphi
• Viewing Presto Data in RAD Studio Data Explorer
• Build a Simple VCL Application for Presto Data