ODBC drivers comply with the ODBC API, meaning that they offer a set of about 80 C functions with well-defined behavior that internally use database-specific commands to achieve the desired behavior. There is some wiggle room that allows ODBC drivers to implement certain things differently or even exclude support for some advanced usage patterns. But in essence, all ODBC drivers are born more or less equal.
ODBC drivers are easy to come by. Major database vendors offer ODBC drivers as free downloads (Microsoft SQL server, Exasol, Teradata, etc). Open source databases provide ODBC databases as part of their projects (PostgreSQL, Impala, MongoDB). Many ODBC drivers are also shipped with Linux distributions or are readily available via Homebrew for OSX. Last but not least, commercial ODBC drivers are available at Progress or easysoft, claiming better performance that their freely available counterparts.
ODBC driver manager¶
The driver manager is a somewhat odd centerpiece. It is a library that can be used just like any ODBC driver. It provides definitions for various data types, and actual ODBC drivers often rely on these definitions for compilation. The driver manager has a built-in configuration of data sources. A data source has a name (the data source name or DSN), is associated with an ODBC driver, contains configuration options such as the database host or the connection locale, and sometimes it also contains credentials for authentication with the database. Finally, the driver manager typically comes with a tool to edit data sources.
Driver managers are less numerous, but still easily available on all major platforms. Windows comes with a preinstalled ODBC database manager. On Linux and OSX, there are competing driver managers in unixodbc and iodbc.
Turbodbc is tested with Windows’s built-in driver manager and unixodbc on Linux and OSX.
Applications finally use the ODBC API and link to the driver manager. Any time they open a connection, they need to specify the data source name that contains connection attributes that relate to the desired database. Alternatively, they can specify all necessary connection options directly.
Linking to the driver manager instead of the ODBC driver directly means that changing to another driver is as simple as exchanging the connection string at runtime instead of tediously linking to a new driver. Linking to the driver manager also means that the driver manager handles many capability and compatibility options by transparently using alternative functions and workarounds as required.