First, you need an ODBC Driver. unixODBC is a driver manager (iODBC is another) written for various *nixes.
The Driver manager is the library you link to. The Manager handles the dynamic loading/unloading of drivers, allowing you access more than one type of datasource. there are several vendors for drivers, and there are some freeware drivers available of varying quality.
I work for a driver vendor. If you need help, we have demo downloads, and tech support to get you running.