This series is based upon SAP HANA on premise and SAP HANA, express edition - HANA 2.0 with XSA and SAP Web IDE for SAP HANA. Originally recorded in January 2019. The previous video was very simplistic because it only exposed one database table as a single entity. Often you need to also represent relationships between multiple entities. For example we might want to build an OData service which has both the Purchase Order Header and Items. For this we would build a 1:many relationship between the two entities.