SharePoint 2010 defines the structure of the external data to which it will connect through external content types. External content types are similar to SharePoint content types that define the structure of the data stored in SharePoint. However, external content types define the structure of the data not stored in SharePoint. In addition external content types define the data access capabilities for the external data source.
For those who worked on Business Data Connectivity in SharePoint 2007, you can consider an external content type to be equivalent to a BDC entity. However, external content types contain much more information compared to a BDC entity.
External lists are lists based on external content types. They help you interact with the external data in the same way as the normal SharePoint list works.
External lists do not physically store data. They are just a medium to interact with the external data.
Follow the next steps to create an external content type and list in SharePoint Designer.
When adding or editing the items in the list, make sure you add data that complies with the database constraints. For example, the ProductSubCategoryID and ProductModelID have foreign key constraints and you need to add one of the valid values that you can pick up by looking at the existing records.