22.1.2.1. General Information About ODBC and Connector/ODBC

Open Database Connectivity (ODBC) is a widely accepted application-programming interface (API) for database access. It is based on the Call-Level Interface (CLI) specifications from X/Open and ISO/IEC for database APIs and uses Structured Query Language (SQL) as its database access language.

A survey of ODBC functions supported by Connector/ODBC is given at Section 22.1.6.1, "Connector/ODBC API Reference". For general information about ODBC, see http://support.microsoft.com/kb/110093.

22.1.2.1.1. Connector/ODBC Architecture

The Connector/ODBC architecture is based on five components, as shown in the following diagram:

Application:

The Application uses the ODBC API to access the data from the MySQL server. The ODBC API in turn communicates with the Driver Manager. The Application communicates with the Driver Manager using the standard ODBC calls. The Application does not care where the data is stored, how it is stored, or even how the system is configured to access the data. It needs to know only the Data Source Name (DSN).

A number of tasks are common to all applications, no matter how they use ODBC. These tasks are:
- Selecting the MySQL server and connecting to it.
- Submitting SQL statements for execution.
- Retrieving results (if any).
- Processing errors.
- Committing or rolling back the transaction enclosing the SQL statement.
- Disconnecting from the MySQL server.
Because most data access work is done with SQL, the primary tasks for applications that use ODBC are submitting SQL statements and retrieving any results generated by those statements.
Driver manager:

The Driver Manager is a library that manages communication between application and driver or drivers. It performs the following tasks:
- Resolves Data Source Names (DSN). The DSN is a configuration string that identifies a given database driver, database, database host and optionally authentication information that enables an ODBC application to connect to a database using a standardized reference.
  
  Because the database connectivity information is identified by the DSN, any ODBC compliant application can connect to the data source using the same DSN reference. This eliminates the need to separately configure each application that needs access to a given database; instead you instruct the application to use a pre-configured DSN.
- Loading and unloading of the driver required to access a specific database as defined within the DSN. For example, if you have configured a DSN that connects to a MySQL database then the driver manager will load the Connector/ODBC driver to enable the ODBC API to communicate with the MySQL host.
- Processes ODBC function calls or passes them to the driver for processing.
Connector/ODBC Driver:

The Connector/ODBC driver is a library that implements the functions supported by the ODBC API. It processes ODBC function calls, submits SQL requests to MySQL server, and returns results back to the application. If necessary, the driver modifies an application's request so that the request conforms to syntax supported by MySQL.
DSN Configuration:

The ODBC configuration file stores the driver and database information required to connect to the server. It is used by the Driver Manager to determine which driver to be loaded according to the definition in the DSN. The driver uses this to read connection parameters based on the DSN specified. For more information, Section 22.1.4, "Configuring Connector/ODBC".
MySQL Server:

The MySQL database where the information is stored. The database is used as the source of the data (during queries) and the destination for data (during inserts and updates).

22.1.2.1.2. ODBC Driver Managers

An ODBC Driver Manager is a library that manages communication between the ODBC-aware application and any drivers. Its main functionality includes:

Resolving Data Source Names (DSN).
Driver loading and unloading.
Processing ODBC function calls or passing them to the driver.

Both Windows and Mac OS X include ODBC driver managers with the operating system. Most ODBC Driver Manager implementations also include an administration application that makes the configuration of DSN and drivers easier. Examples and information on these managers, including Unix ODBC driver managers, are listed below:

Microsoft Windows ODBC Driver Manager (odbc32.dll), http://support.microsoft.com/kb/110093.
Mac OS X includes ODBC Administrator, a GUI application that provides a simpler configuration mechanism for the Unix iODBC Driver Manager. You can configure DSN and driver information either through ODBC Administrator or through the iODBC configuration files. This also means that you can test ODBC Administrator configurations using the iodbctest command. http://www.apple.com.
unixODBC Driver Manager for Unix (libodbc.so). See http://www.unixodbc.org, for more information. The unixODBC Driver Manager includes the Connector/ODBC driver 3.51 in the installation package, starting with version unixODBC 2.1.2.
iODBC ODBC Driver Manager for Unix (libiodbc.so), see http://www.iodbc.org, for more information.