ADOQuery (C++)

Description

This example demonstrates the use of ADO for database connectivity. The example assumes that a TDBGrid is placed on the form.

Code

__fastcall TForm2::TForm2(TComponent* Owner)
        : TForm(Owner)
{
        /* Login details */
        String UserName = "db_user_name";
        String PassWord = "db_pass_word";
        String Server = "my.db.server";
 
        /* Connection String */
        String ConnString =
                "Provider=SQLOLEDB.1;Persist Security Info=False;";
        ConnString +=
                "User ID=%s;Password=%s;Data Source=%s;Use Procedure for Prepare=1;";
        ConnString +=
                "Auto Translate=True;Packet Size=4096;Use Encryption for Data=False;";
        ConnString +=
                "Tag with column collation when possible=False";
 
        /* SQL Query */
        String SQLStr = "SELECT * FROM customer WHERE customer_id = :AnId;";
 
        /* All ADO variables */
        TADOConnection* ADOConn;
        TADOQuery* ADOQuery;
        TDataSource* DataSrc;
        TParameter* Param;
        /* Create an ADO connection. */
        ADOConn = new TADOConnection(this);
 
        /* Set up the connection string. */
        ADOConn->ConnectionString = Format(ConnString,
                ARRAYOFCONST((UserName, PassWord, Server)));
 
        /* Disable login prompt. */
        ADOConn->LoginPrompt = False;
 
        try
        {
                ADOConn->Connected = true;
        }
        catch (EADOError& e)
        {
                MessageDlg("Error while connecting", mtError,
                                          TMsgDlgButtons() << mbOK, 0);
                return;
        }
 
        /* Create the query. */
        ADOQuery = new TADOQuery(this);
        ADOQuery->Connection = ADOConn;
        ADOQuery->SQL->Add(SQLStr);
 
        /* Update the parameter that was parsed from the SQL query: AnId. */
        Param = ADOQuery->Parameters->ParamByName("AnId");
        Param->DataType = ftInteger;
        Param->Value = 1;
 
        /* Set the query to Prepared--it will improve performance. */
        ADOQuery->Prepared = true;
 
        try
        {
                ADOQuery->Active = true;
        }
        catch (EADOError& e)
        {
                MessageDlg("Error while connecting", mtError,
                                          TMsgDlgButtons() << mbOK, 0);
                return;
        }
 
        /* Create the data source. */
        DataSrc = new TDataSource(this);
        DataSrc->DataSet = ADOQuery;
        DataSrc->Enabled = true;
 
        /* Finally, initialize the grid. */
        DBGrid1->DataSource = DataSrc;
}

Uses

• Data.Win.ADODB.TADOConnection ( fr | de | ja )
• Data.Win.ADODB.TADOQuery ( fr | de | ja )
• Data.Win.ADODB.TParameter ( fr | de | ja )
• Data.Win.ADODB.TADOConnection.ConnectionString ( fr | de | ja )
• Data.DB.TCustomConnection.LoginPrompt ( fr | de | ja )
• Data.DB.TCustomConnection.Connected ( fr | de | ja )
• Data.Win.ADODB.TCustomADODataSet.Parameters ( fr | de | ja )
• Data.Win.ADODB.TCustomADODataSet.Connection ( fr | de | ja )
• Data.Win.ADODB.TADOQuery.SQL ( fr | de | ja )
• Data.Win.ADODB.TCustomADODataSet.Prepared ( fr | de | ja )