Types of Joins

If an object class A references the object class B, a relation exists between objects of both classes. But there are normally also objects of object class A that do not reference object of the object class B and objects of the object class B that are not referenced by object class A.

If you join an object class to your base object class in the Alfabet query, you can use four different kind of JOINS to select a different subset of objects:

InnerJoin	FullJoin	LeftJoin	RightJoin
Selects all instances from both classes that are related to each other	Selects all instances from both classes	Selects all instances from both classes that are related to each other and all instances from A that do not have a reference to B.	Selects all instances from both classes that are related to each other and all instances from B that are not referenced by A.