Working with Query Keys

Use a direct query key as an alias for a field name. Query keys allow TopLink expressions to refer to a field using Java attribute names (such as firstName), rather than DBMS-specific names (such as F_NAME).

Use query keys to:

Enhance code readability when defining TopLink expressions.
Increase portability by making code independent of the database schema. If you rename a field, the query key could be redefined without changing any code that references it.
Interface descriptors define only common query keys shared by implementors; the fields aliased could have different names in the implementor's tables.