As a feature request can c3p0 instead of requiring the user to enter the preferredTestQuery, supply a preferredTestQuery for each driver? If the user wants to override the preferredTestQuery the option is still there, though it would be nice to have a default.

For instance
# for MySQL/PostgreSQL/MS SQL use: SELECT 1 
# for Oracle use: SELECT 1 from dual 
# for DB2 use: SELECT 1 FROM sysibm.sysdummy1