Does a JDBC driver's version and a DB's version have to match exactly?

Question

Say I have postgresql 9.1 running on a server, yet I choose to use a 9.2 driver to access it. Would this work? If not, are these version checks always enforced, or does it depend on your DBMS?

Answer 1

Not mandatory.
Drivers can support multiple versions of RDBMS, or just only specific one, it depends.
Usually every drivers come out with compatibility table to let you choose most recent driver version (usually with bugfixes, improvements, ...) against your RDMBS version or just the latest drivers compatible with your RDBMS for legacy scenario.

http://jdbc.postgresql.org/download.html

This is the current version of the driver. Unless you have unusual requirements (running old applications or JVMs), this is the driver you should be using. It supports Postgresql 7.2 or newer and requires a 1.5 or newer JVM. It contains support for SSL and the javax.sql package. It comes in two flavours, JDBC3 and JDBC4. If you are using the 1.6 or 1.7 JVM, then you should use the JDBC4 version.