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Direct SQL Calls With ODBC and STL

Thursday Jan 3rd 2002 by Ian Duff

Calling SQL with the STL.

I looked at Dave Merner's article on direct SQL calls with ODBC and some subsequent correspondence regarding non MFC class usage. Some readers were interested in an STL solution and I have made the following changes to the presented code:
  • The CPtrArray has been replaced by a standard STL vector.
  • The Column classes have been coded to orthodox canonical form of class for STL usage.
  • Many of the ODBC calls are deprecated and have been replaced with later ODBC function calls.
  • The demo project contains some example code usage.
  • Worthwhile reader contributions have been applied to the code.

The code and project require a DSN to the MS Northwind sample database in order to run correctly and this short article is offered as a technique for using simple STL container classes and ODBC.

Thanks to all at codeguru for sharing code and ideas.

Example code usage also available in the demo project:

try {
  cout << "Connecting to Sample Northwind database..." << endl;
  CIDSQLDirect sqlDirect;     // Our direct ODBC class

  if (( nRetCode = sqlDirect.Connect("Northwind") ) != SQL_SUCCESS )
     return( nRetCode );

  if (( nRetCode = sqlDirect.ExecuteSQL("SELECT COUNT(*) FROM Employees"))
              != SQL_SUCCESS )
     return( nRetCode );

  if (( nRetCode = sqlDirect.Fetch() ) != SQL_SUCCESS )
     return( nRetCode );  // Fetch the result from this COUNT(*)

  string strFetch = sqlDirect.GetCol( 1 );
  cout << "Employees Table contains (" << strFetch << ") entries" << endl;

  // This query returns all data in the Employees table
  if (( nRetCode = sqlDirect.ExecuteSQL("SELECT * FROM Employees"))
              != SQL_SUCCESS )
     return( nRetCode );

  int nColumns = sqlDirect.GetNumColumns();
  cout << "Query returned (" << nColumns << ") columns" << endl;
  sqlDirect.PrintColumnNames();
  DisplayData( sqlDirect ); // Print the information now contained
  }

catch( ... ) {
  cout << "SQL Exception Caught!" << endl;
}

Downloads

Download demo project - 26 Kb
Download source - 9 Kb
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