Represents relational constraints that can be used in database
query "where clauses". Instances of QueryExp are returned by the
static methods of the Query
class.
It is possible, but not
recommended, to create custom queries by implementing this
interface. In that case, it is better to extend the QueryEval
class than to implement the interface directly, so that
the QueryExp.setMBeanServer(javax.management.MBeanServer)
method works correctly.