在AE中创建关系类（RelatinshipClass）的三种不同方式

1. Relationship Class � If you want to create a relationship class to store the relationship within a geodatabase (any type of geodatabase) you can use IFeatureWorkspace.CreateRelationshipClass or IRelationshipClassContainer.CreateRelationshipClass. However it is important to note that if you want to use a relationship class, it can only relate feature classes and or tables that reside within the same Geodatabase.

所有表必须在同一数据库中，关系类在数据库中持久化

2. In Memory Relationship Class � If you only want the relationship to persist while your code is running you can use an in memory relationship class. IMemoryRelationshipClassFactory.Open can be used to create the temporary relationship class. Since the relationship class is not permanently stored in a Geodatabase you can use the in memory relationship class to relate data that is stored in different locations and of different types. For example you can use an in memory relationship class to relate a feature class to a shapefile or another feature class in a different geodatabase.

不同源表数据创建关联使用内存管理类，其关系不在数据中持久化，但可以保存在mxd中

3. Joins � You can also use IRelQueryTableFactory.Open to create a join between two tables. Joins can be used to associate data that is stored in different locations and of different types as well. With a RelQueryTable the associate is based on a RelationshipClass or MemoryRelationshipClass.

创建两个表之间的关系