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: August 27, 2015 With the cloud enabling companies to spin up servers and stand up data stores more quickly, mobile apps can be created faster, reducing the time-to-value. But three major obstacles stand in the way for many organizations: The backlog of app project requests confronting every enterprise regardless of their internal app development capabilities Finding and employing better, faster tools to speed and simplify the process of developing those apps. The emergence of …

  • Live Event Date: September 23, 2015 @ 1:00 p.m. ET / 10:00 a.m. PT The cloud is not just about a runtime platform for your projects – now, you can do your development in the cloud, too. Check out this upcoming eseminar to learn how the cloud improves your development experience and team collaboration. Join Dana Singleterry, Principal Product Manager for Oracle Dev Tools, as he discusses how to simplify every aspect of the development lifecycle, including requirements gathering, version management, code …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date