Open Database Connectivity

Mr. Harvey describes the ODBC open specification for application developers.

Open Database Connectivity (ODBC) is an open specification for providing application developers with a predictable application programmers interface (API) with which to access data sources. Data sources can be just about anything, provided someone has created an ODBC driver for it. The most common data source is an SQL server.

The two major advantages of coding an application with the ODBC API are portable data access code and dynamic data binding.

Portable Data Access Code

The ODBC API (or CLI, command-line interface), as outlined by X/Open and the ISO, is available on all major platforms. Microsoft platforms include many enhancements to this specification. The current version from Microsoft is 3.51. The idea is that a programmer using the ODBC API is likely to have data access code which is portable to other platforms. The same code will also be portable across different data sources. For example, data for an accounting program application can reside on a light SQL server during development and then be moved over to a heavy SQL server just by linking to a different ODBC driver. ODBC delivers platform and data source portability.

Dynamic Binding

Dynamic binding allows the user or the system administrator to easily configure an application to use any ODBC-compliant data source. This is the single biggest advantage of coding an application with the ODBC API and purchasing such an application. Dynamic binding allows the end user to pick a data source, e.g., an SQL server, and use it for all data applications. Applications do not have to be recompiled or recoded for the new target data source. This is achieved by the ODBC Driver Manager which will pass the ODBC calls to the user's ODBC driver without the need to relink the code. ODBC enables the user to choose where the data will be stored.

unixODBC Project

The unixODBC Project's goals are to develop and promote unixODBC as the definitive standard for ODBC on the Linux platform. This is to include Microsoft extensions, where they make sense, and GUI clients. The unixODBC team is achieving this objective by providing the best technical solution to ODBC demands on the Linux platform. All unixODBC development is released under GPL or LGPL.

The components of this project are the Driver Manager, DataManager, ODBCConfig, Odbcinst, drivers and other utilities.

Driver Manager

Figure 1. Libraries

This share library is the hub of most ODBC activity, but its function is simple. Ninety percent of the Driver Manager's function is to validate arguments, load and unload drivers and pass the call to the driver in a manner consistent with the ODBC specification. Normally, an application links only to this share to get the ODBC support it requires (see Figure 1). The Driver Manager loads/unloads the appropriate driver and passes calls to the driver.

DataManager

Figure 2. DataManager TreeView

This is a GUI-client utility. The current version is based upon Troll Tech's Qt class library (http://www.troll.no/). The DataManager allows the user to browse and manage data sources (see Figure 2). The right side of the TreeView contains a sizable canvas which can be extended to include properties for any TreeView selections. An example of this has been implemented for the data source TreeViewItem. When a data source is selected, the canvas becomes a handy editor which can be used to submit SQL, review results and save/load either SQL or the results. Table designers and data editors could be easily added to the DataManager using the same techniques. The DataManager is an easy way to manage ODBC data-source resources.

ODBCConfig

Figure 3. ODBC Data Source Administrator

This is another GUI-client utility. It has been created to be user compatible with the Microsoft ODBC administration utility (see Figure 3). ODBCConfig makes it easy, even for non-techies, to configure their data sources. ODBCConfig uses the Odbcinst library to read/write ODBC system information. ODBCConfig will make use of any installed driver configuration libraries to present a list of driver-specific options to edit. ODBCConfig functionality is an excellent candidate for the KDE (http://www.kde.org/) Control Center. ODBCConfig makes it easy to configure ODBC data sources.

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