OLE DB Templates - A light and simple Data Access Method

I was amazed and delighted to see how simple database access has become thanks to OLE DB. I've been reading the hype and so I went out and found the Microsoft Book on OLE DB. It's a great idea as it's explained there but still rather complex to code. I noticed that Visual C++ 6 has some new templates for Data Consumers so I started looking at the documentation. Wow! Is this simple stuff or what??

Here's a sample, a CONSOLE application at that, using the NWind database that comes with the DASDK. It's only 99 lines of code including comments and it compiles into a 60K executable.


 
//file: olsamp.cpp 
//auth: dick warg 
//date: 6/25/99 
//func: minimal oledb program

#include <atldbcli.h>
#include <iostream>
using namespace std;

// define a class to hold the data from the table
class myNwCust
{
public:
    // data elements
    TCHAR m_CustomerID[6];
    TCHAR m_CompanyName[41];
    TCHAR m_ContactName[31];
    TCHAR m_Phone[25];

    // column binding  -- I only want these 4 fields
    BEGIN_COLUMN_MAP(myNwCust)
        COLUMN_ENTRY(1, m_CustomerID)
        COLUMN_ENTRY(2, m_CompanyName)
        COLUMN_ENTRY(3, m_ContactName)
        COLUMN_ENTRY(4, m_Phone)
    END_COLUMN_MAP()
};

// declare the OLEDB objects
CDataSource ds;
CSession    session;
CCommand <CAccessor<myNwCust> > cust;

int main()
{

try{
    // fire up COM
    HRESULT hr = CoInitialize(0);
    if(FAILED(hr))
    {
        cout << "Can't start COM!? " << endl;
        return -1;
    }
    
    // connect to the database
    hr = ds.Open(_T("MSDASQL"), "OLE_DB_NWind_Jet", "sa", "");
    if(FAILED(hr))
    {
        cout << "Can't open Nwind" << endl;
        return -1;
    }

    // start the session
    hr = session.Open(ds);
    if(FAILED(hr))
    {
        cout << "Can't open Nwind SESSION" << endl;
        ds.Close();
        return -1;
    }

    // construct the query string
    TCHAR mySQL[] = "SELECT CustomerID, CompanyName, ContactName, \
    Phone FROM Customers";

    // open the dataset
    hr = cust.Open(session, mySQL);
    if(FAILED(hr))
    {
        cout << "Can't open Nwind TABLE" << endl;
        session.Close();
        ds.Close();
        return -1;
    }

    // read all the data
    while(cust.MoveNext() == S_OK)
    {
        cout << cust.m_CustomerID << ", " << cust.m_CompanyName << ", "; 

        cout << cust.m_ContactName << ", " << cust.m_Phone << endl;
    }

    cust.Close();
    session.Close();
    ds.Close();

    cout << "That's All Folks" << endl;

    return 1;
}
catch(...)
{
    cout << "Unknown failure" << endl;
    return -1;
}
}

The Microsoft documentation and samples are in the MSDN pages "Visual C++ Documentation \ References \ Microsoft Foundation Class Library and Templates\OLE DB Templates"


Comments

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • On-demand Event Event Date: September 10, 2014 Modern mobile applications connect systems-of-engagement (mobile apps) with systems-of-record (traditional IT) to deliver new and innovative business value. But the lifecycle for development of mobile apps is also new and different. Emerging trends in mobile development call for faster delivery of incremental features, coupled with feedback from the users of the app "in the wild." This loop of continuous delivery and continuous feedback is how the best mobile …

  • Targeted attacks and advanced threats are customized to infiltrate your unique IT infrastructure, evade conventional defenses, and remain hidden while stealing your corporate data. To detect these criminal intrusions, analysts and security experts agree that organizations should deploy advanced threat protection as part of an expanded security monitoring strategy. For this comparative analysis of breach detection systems, product analysis reports and comparative analysis reports are used to create the security …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds