HOWTO: Create an .MDB File for Microsoft Access Databases

ID: Q118609

The information in this article applies to:

The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1

SUMMARY

NOTE: For information about how to create .MDB files programmatically using Visual C++ version 4.x or later, please see the following article in the Microsoft Knowledge Base:

Q126606 INFO: Accessing CREATE_DB, REPAIR_DB, and COMPACT_DB

An .mdb file is always required to configure a Microsoft Access data source either by using the Open Database Connectivity (ODBC) administrator or by configuring the data source programmatically. An .mdb file cannot be created by using the MFC Database Classes or the ODBC application programming interface (API).

You can use one of the following methods to have an application configure a data source on your computer:

Ship and install the .mdb file along with the application.

Make the .mdb file into a user-defined resource. Then, copy the .mdb file at run time.

This article discusses the second method, making the .mdb file into a user- defined resource.

MORE INFORMATION

You can use a user-defined resource to attach miscellaneous data to a .EXE file. If an .mdb file is made into a resource, the resource can be loaded at run time and then written to an .mdb file. The steps required to do this are as follows:

Create an .mdb file either by using Microsoft Access or MSQuery.

Create the .mdb file as a user-defined resource by adding the following line to your .RC file:


      mdb_file  MDB_RESOURCE filename.mdb

where:


      mdb_file      is  a name for identifying the resource.
      MDB_RESOURCE  is  a name for identifying the type of the resource
                        and can be any user-defined type.
      filename.mdb  is  the name of the .mdb file.

Load the resource and write it out to an .mdb file. You can use the following function, from anywhere in your application, to create the .mdb file. (A typical place for creating the .mdb file would be the override of the CWinApp::InitInstance() function.)


   CreateMDBFile()
   {
      // Get the instance handle - required for loading the resource
      HINSTANCE hInst = AfxGetInstanceHandle();

      // Load the user-defined resource.
      HRSRC hmdbFile = ::FindResource(hInst, "mdb_file", "MDB_RESOURCE");
         HGLOBAL hRes = ::LoadResource(hInst, hmdbFile);
         DWORD dwResSize = ::SizeofResource(hInst, hmdbFile);

         if (hRes != NULL)
         {
            UINT FAR* lpnRes = (UINT FAR*)::LockResource(hRes);
            CString szFileName = "Filename.mdb";

            TRY
            {
               // Create the .mdb file
               CFile f( szFileName, CFile::modeCreate | CFile::modeWrite );

               // Write the user-defined resource to the .mdb file
               f.WriteHuge(lpnRes, dwResSize);
               f.Flush();
            }
            CATCH( CFileException, e )
            {
      #ifdef _DEBUG
             afxDump << "File could not be opened " << e->m_cause << "\n";
      #endif
            }
            END_CATCH

      #ifndef WIN32 //Unlock Resource is obsolete in the Win32 API
            ::UnlockResource(hRes);
      #endif
            ::FreeResource(hRes);
         }
      }

The one disadvantage of this method is that it increases the size of the .exe file according to the size of the .mdb file. Because even an empty .mdb file is 64K in size, the .exe is increased by at least 64K. One way to reduce the size of the .exe is to store a compressed .mdb file onto the .exe and expand it at run time when storing the resource.

REFERENCES

For more information on user-defined resources, refer to the Windows SDK Help.

For additional information on configuring a data source programmatically, please see the following articles in the Microsoft Knowledge Base:

Q110507 HOWTO: Configure ODBC Data Sources on the Fly

Q110508 HOWTO: Create Tables with Foundation Database Classes

Additional query words: 2.50 2.51 2.52 3.00 3.10 ODBC

Keywords : kbprg kbDatabase kbMFC kbODBC kbVC
Version : 1.5 1.51 1.52 2.0 2.1
Platform : NT WINDOWS
Issue type : kbhowto