Sun Java System Application Server Platform Edition 8.2 Developer's Guide

Fixed Length CHAR Primary Keys

If an existing database table has a primary key column in which the values vary in length, but the type is CHAR instead of VARCHAR, the Application Server automatically trims any extra spaces when retrieving primary key values. It is not a good practice to use a fixed length CHAR column as a primary key. Use this feature with schemas that cannot be changed, such as a schema inherited from a legacy application.