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

  • Java developers know that testing code changes can be a huge pain, and waiting for an application to redeploy after a code fix can take an eternity. Wouldn't it be great if you could see your code changes immediately, fine-tune, debug, explore and deploy code without waiting for ages? In this white paper, find out how that's possible with a Java plugin that drastically changes the way you develop, test and run Java applications. Discover the advantages of this plugin, and the changes you can expect to see …

  • Live Event Date: August 20, 2014 @ 1:00 p.m. ET / 10:00 a.m. PT When you look at natural user interfaces as a developer, it isn't just fun and games. There are some very serious, real-world usage models of how things can help make the world a better place – things like Intel® RealSense™ technology. Check out this upcoming eSeminar and join the panel of experts, both from inside and outside of Intel, as they discuss how natural user interfaces will likely be getting adopted in a wide variety …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds