changing variable types of a function of a derived class

Hello,

I have a class that uses some variables to access a sql database, and I want to make a derived class that inherits all the methods of this class, because the derived one will do exactly the same process that the parent one, but with a postgres database, thus I've got to use diferent type variables to acces the database.

There's one big function in the class that does all the DB stuff, and I want to know if there's any way to inherit the function but with only changing the type of some vars inside this function.

Thanks!

Sergi