HOWTO: Configure ODBC Data Sources on the Fly

ID: Q110507

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, 2.2, 4.0, 4.1, 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2

SUMMARY

You can configure ODBC (Open Database Connectivity) data source names programmatically. This gives you flexibility to export data without forcing the user to explicitly use the ODBC Administrator or other programs to specify the names of data sources. This might, for example, enable your program to use the ODBC API (application programming interface) to export an .XLS file. To do this, use the SQLConfigDataSource() function.

The following example uses SQLConfigDataSource to create a new Excel data source called "New Excel Data Source":


   SQLConfigDataSource(NULL,ODBC_ADD_DSN,
     (LPSTR) "Excel Files (*.xls)",
     (LPSTR) "DSN=New Excel Data Source\0"
     "Description=New Excel Data Source\0"
     "FileType=Excel\0"
     "DataDirectory=C:\\EXCELDIR\0"
     "MaxScanRows=20\0");

Note that the data source is actually a directory (C:\EXCELDIR). The Excel driver has directories as its data sources, and files as the individual tables (one table per .XLS file).

For additional information on creating tables, please see the following article(s) in the Microsoft Knowledge Base:

Q110508 Creating Tables with Foundation Database Classes

The information below discusses the parameters that need to be passed to the SQLConfigDataSource() ODBC API function. To use the SQLConfigDataSource() function, you must include the ODBCINST.H header file and use the ODBCINST.LIB import library.

NOTE: For 32-bit applications, you must still include ODBCINST.H header file, however you must now link with ODBCCP32.lib

NOTE: The information contained within this article is duplicated in the 'Programming with MFC Encyclopedia' shipped with Visual C++ 4.0. The article can be found by searching for "SQLConfigDataSource" and selecting the article titled 'FAQ: Programatically Configuring an ODBC Data Source'.

MORE INFORMATION

NOTE: This article was originally written for the 16-bit ODBC components only. The 16-bit ODBC components use INI files to store information on configured datasources (ODBC.INI) and installed drivers (ODBCINST.INI). The 32-bit ODBC components no longer use INI files but, instead, write such information to the registry. System datasource information and installed driver information is stored in HKEY_LOCAL_MACHINE\SOFTWARE\ ODBC\ in ODBC.INI and ODBCINST.INI, respectively. Non-System datasources are stored in HKEY_CURRENT_USER\SOFTWARE\ODBC\ODBC.INI. In the remainder of this article, references to ODBC.INI should be interpreted as referring to the appropriate section of the registry if you are using the 32-bit ODBC components.

An ODBC data source name can be created using the ODBC Administrator program or similar utility. However, sometimes it is desirable to create a data source name directly from your application so that access can be obtained without requiring the user to run a separate utility.

The ODBC Administrator (typically installed in the Windows Control Panel) creates a new data source by putting entries in the ODBC.INI file. This file is queried by the ODBC Driver Manager to obtain the required information about the data source. It's important to know what information needs to be placed in the ODBC.INI because you'll need to supply it with the call to SQLConfigDataSource().

Although this information could be written directly to the ODBC.INI file [without using SQLConfigDataSource()], any application that does this is relying on the current technique that the Driver Manager uses to maintain its data. If a later revision to the ODBC Driver Manager implements record keeping about data sources in a different way, then any application that used this technique would be broken. It is generally advisable to use an API function when one is provided.

Below, you will find an explanation of the parameters of the SQLConfigDataSource() function. Much of the information is taken from the ODBC API Programmer's Reference supplied with Visual C++ version 1.5.

Function prototype:
   BOOL SQLConfigDataSource(HWND hwndParent,UINT fRequest,
                            LPCSTR lpszDriver,
                            LPCSTR lpszAttributes); 
hwndParent - This is the window that will be used as the owner of any dialog boxes which are created by either the Driver Manager or the specific ODBC Driver to obtain additional information from the user about the new data source. If there is not enough information provided in the lpszAttributes parameter, a dialog box will appear. This parameter may be NULL, see the reference for specifics.

fRequest - The operation to be performed. Possible values are:
                      ODBC_ADD_DSN: Add new user data
                        source.
                      ODBC_CONFIG_DSN: Modify an
                        existing data source.
                      ODBC_REMOVE_DSN: Remove an
                        existing data source. 
The following are available in ODBC 2.5 32 bit only:
                      ODBC_ADD_SYS_DSN: Add a new
                        system data source.
                      ODBC_CONFIG_SYS_DSN: Modify
                        an existing system data
                        source.
                      ODBC_REMOVE_SYS_DSN: Remove
                        an existing system data
                        source. 
lpszDriver - Driver description. As the documentation mentions, this is the name presented to the users rather than the physical driver (the DLL). You can determine the description of a driver using the ODBC Administrator program as follows:

Run the ODBC Administrator program.

Choose Add. This will give you a list of installed drivers.

The list contains driver descriptions. It is this description that you will use as the lpszDriver parameter. Note that the ENTIRE description is used [for example, "Excel Files (*.xls)"] including the file extension and parentheses if they exist in the description.

Optionally, you can examine the file ODBCINST.INI, which contains a list of all driver entries and descriptions in the section [ODBC Drivers].

lpszAttributes - List of attributes in the form "keyname=value". These strings are separated by null terminators with two consecutive null terminators at the end of the list. These attributes will primarily be default driver-specific entries, which go into the ODBC.INI file for the new data source. One important key, which is not mentioned in the ODBC API reference for this function, is "DSN" which specifies the name of the new data source. The rest of the entries are specific to the driver for the new data source. Often times it is not necessary to supply ALL of the entries because the driver can prompt the user (if hwndParent is not NULL) with dialog boxes for the new values. You might want to explicitly supply default values so that the user is not prompted.

One way to find the keynames and their values is to examine the ODBC.INI file for an already configured data source (perhaps one that has been configured by the ODBC Administrator program):

Open the ODBC.INI file.

Find the section marked by [<data source name>] where <data source name> is a data source that has already been configured with the desired settings for the driver you intend to use. The lines following this line will be of the form "keyname=value". These are exactly the entries you will want to use in your lpszAttributes parameter.

You might also want to examine the documentation for the specific driver you are going to use. Useful information may be found in the online help for the driver, which can be accessed by running the ODBC Administrator: click Add, select the driver name, and click OK. When the information for creating a new data source comes up for that particular driver, select Help. This will open the help file for that particular driver, which generally contains important information concerning the use of the driver.

REFERENCES

ODBC Programmer's Reference and SDK Guide (available in Books Online).

Additional query words: datasource

Keywords : kbDatabase kbMFC kbODBC kbVC
Version : 1.5 1.51 1.52 2.0 2.1 2.2 4.0
Platform : NT WINDOWS
Issue type :