Thanks Christian.

Can you tell me if how does hibernate behave if the actual database contains more columns than the mapping file indicates?

For example, in the mapping file, I map 4 attributes of my class.
First I have 4 columns in my table for that class.

What if I use the "alter" command and add an extra column in my table (or any mis-match between the actual database table and the mapping), will hibernate still work (i.e. able to retrieve the java object correctly)?

Thank you.

If you don't map a column then Hibernate does not even know it exists. If it not nullable without a default then the database JDBC driver will complain etc. If its nullable plain column then it will not be an issue.