Say I create a function cal_diff(arg0 number, arg1 number) in Oracle 10g, could I use it in HQL?

for example in HQL: from Something t where t.someValue < cal_diff(t.val1, t.val2)

I am sorry if it's obviously covered in the documentation, though I can't find anywhere it talks about this capability. Any help would be appreciated. Thanks.

It is possible to register other SQL functions with Hibernate and use them with HQL. As mentioned in http://docs.jboss.org/hibernate/stable/ ... -functions this is an area that needs improvement. The usual way to solve this is to subclass an existing Dialect implementation and add definitions for your extra functions there. It is not very difficult but is a bit messy if you need to support multiple databases.

Another approach (that I prefer) is to register the function using the Configuration.addSqlFunction() method.