web server - Borland Technical Publications

Implementing an entity bean
Generating primary keys from a custom class
To generate primary keys from a custom class, you must write a class that implements
the com.borland.ejb.pm.PrimaryKeyGenerationListener interface.
Support for composite keys
Primary keys are not restricted to a single column. Sometimes, a primary key is
composed of more than one column. In a more realistic example, a course is not
identified merely by its name. Instead, the primary key for each course record can be
the department in which the course is offered and the course number itself. The
department code and the course number are separate columns in the Course table. A
select statement that retrieves a particular course, or all courses in which a student is
enrolled, must use the entire primary key; that is, it must consider both columns of the
primary key.
The Borland CMP engine supports composite primary keys. You can use keys with
multiple columns in the where clause of a select statement. You can also select all
fields of a compound key in the select clause portion of the statement.
For the where clause, specify multiple field names in the same manner that you specify
single field names. Use “and” to separate each field. The format is
= :[ejb/]
Note that the equal (=) sign is one of several possible notations. You could also specify
greater than (>), less than (=), or less than or equal (