What Is ODBC?

The Open Database Connectivity (ODBC) interface by Microsoft allows applications to access data in database management systems (DBMS) using SQL as a standard for accessing the data. ODBC permits maximum interoperability, which means a single application can access different DBMS. Application end users can then add ODBC database drivers to link the application to their choice of DBMS.

The ODBC interface defines:

A library of ODBC function calls of two types:
Core functions that are based on the X/Open and SQL Access Group Call Level Interface specification
Extended functions that support additional functionality, including scrollable cursors
SQL syntax based on the X/Open and SQL Access Group SQL CAE specification (1992)
A standard set of error codes
A standard way to connect and logon to a DBMS
A standard representation for data types

The ODBC solution for accessing data led to ODBC database drivers, which are dynamic-link libraries on Windows and shared objects on UNIX and Linux. These drivers allow an application to gain access to one or more data sources. ODBC provides a standard interface to allow application developers and vendors of database drivers to exchange data between applications and data sources.

How Does It Work?

The ODBC architecture has four components:

An application, which processes and calls ODBC functions to submit SQL statements and retrieve results
A Driver Manager, which loads drivers for the application
A driver, which processes ODBC function calls, submits SQL requests to a specific data source, and returns results to the application
A data source, which consists of the data to access and its associated operating system, DBMS, and network platform (if any) used to access the DBMS

The following figure shows the relationship among the four components:

Why Do Application Developers Need ODBC?

Using ODBC, you, as an application developer can develop, compile, and ship an application without targeting a specific DBMS. In this scenario, you do not need to use embedded SQL; therefore, you do not need to recompile the application for each new environment.