## 5.5.2.5 Composite Primary Keys

GORM supports the concept of composite identifiers (identifiers composed from 2 or more properties). It is not an approach we recommend, but is available to you if you need it:

    class Person {
      String firstName
      String lastName  static mapping = {
          id composite:['firstName', 'lastName']
      }
    }

The above will create a composite id of the `firstName` and `lastName` properties of the Person class. When you later need to retrieve an instance by id you have to use a prototype of the object itself:

    def p = Person.get(new Person(firstName:"Fred", lastName:"Flintstone"))
    println p.firstName