Use the BCS Data Aggregation sample with BCS in SharePoint Server 2010 and to aggregate data from two external systems.
Learn how to use Business Connectivity Services (BCS) to create associations between external content types in SharePoint Designer 2010 without using code.
Learn to implement your own custom item event handlers and bind them to a site content type or a list.
Learn to implement your own custom list event handlers and bind them to a list type, list instance, site content type, or list content type.