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Professional database modeling


Chapter 13

ODBC

About this chapter

This chapter describes Open Database Connectivity(ODBC).

Open Database Connectivity (ODBC) is the most common method to access data when an application needs to be able to work with databases from many different vendors.

All major database vendors provide a way to access their database through the use of ODBC. All Microsoft Windows machines have an ODBC sub-system installed by default and ODBC is availible for all major operating systems. Most Linux distributions have ODBC (usually unixODBC) but it may not be installed by default.

ODBC must exist in order for Byte Designer to be able to connect to any database.

This brief document provides a quick start to understanding and using ODBC - it is not meant to be a substitute for the ODBC documentation which comes with an ODBC sub-system.

Linux
There are several ODBC sub-systems availible for Linux. The two most popular are; iODBC and unixODBC. One or both of these are probably in your favourite Linux distribution but may not be installed by default. unixODBC is recommended because development is done using unixODBC, and because it has several drivers to get things started. We provide a setup binary in order to chnage between iODBC and unixODBC.
XP
MS Windows has been shipping with an ODBC sub-system for years. It is well documented and fairly complete. MS even includes several drivers.
osx
Apple has never had very good support for ODBC. iODBC installed by default may be required to be patched with fixes from www.iodbc.org. OSX 10.5 is required.

Driver

ODBC Drivers provide the 'glue' which allows the application to communicate with the data source - just as a Printer driver allows the application to communicate with the Printer. This means that an ODBC driver must be installed AND registered before the application can access the data source. Unfortunately; how a driver is installed varies widely depending upon the vendor and platform. You will have to refer to your driver documentation for more information.

Drivers are usually provided by the database vendor and are usually included with the database system. However; in some cases you should get your driver from another source. This is sometimes the case when the 'other' source provides a better driver or a driver bundle.

Data Source Name (DSN)

An application can access the data source by talking directly to the driver but most applications expect to use a DSN. A DSN is a name (used to refer to the data source) and a few settings such as; server name, database etc. The settings vary slightly between drivers so you may want to check with the drivers documentation for details.

Most ODBC sub-systems have a graphical tool to aid in creating a DSN. Some ODBC sub-systems have command-line tools for advanced Users. 

ODBC Administrator

The ODBC Administrator is a graphical tool which aids the User in configurating the ODBC sub-system. Common tasks are;

  • register/unregister a driver
  • create/edit/delete a DSN
  • set ODBC options

linux
Linux machines running the unixODBC sub-system have several methods to register an installed driver and manage data source names. They are listed here in order of ease of use; ODBCConfig, odbcinst, and a text editor. Refer to the unixODBC (www.unixodbc.org) documentation for details. Note: Some Linux distros (such as RedHat) have several RPM's for unixODBC - if possible install all of them.
windows
MS Windows Users should use the ODBC Administrator to manage drivers and data source names. This program can be found in the 'Control Panel'.
osx
ODBC Administrator that cames with the driver manager(iODBC).

Byte Designer has a menu item and toolbar button odbc to quickly access your systems ODBC Administrator. This allows the User to quickly and easily manage drivers and data source names with a familiar tool. Figure 1 shows the ODBC Administrator.

ODBC Config
figure 1
ODBC Administrator

Browse ODBC Sub-System

Byte Designer contains an ODBC Browser. This feature can be used to browse the ODBC sub-system on your machine. This can be helpful when debugging problems with your ODBC sub-system or just to learn more about what is availible in your ODBC sub-system and data sources.

ODBC Browser
figure 2
ODBC Browser

ODBC Bridge



An ODBC Bridge allows software to communicate to a data source using a driver which resides on another machine - usually on a different operating system. For example; someone may be using an application on OSX and have not been able to find an ODBC driver for their database which works on OSX. In this case you install a driver on, for example, XP and use a bridge driver on OSX. The bridge driver looks like a regular ODBC driver to the OSX application but is really acting as a type of relay to the XP machine where the calls make their way to the desired ODBC driver.

See Easysoft

Virtual Server



A Virtual Server ties together more than one data source. An application uses an ODBC driver for the Virtual Server to communicate with all of the databases as if they are a single database.

Resources