This video discusses the concept of associations in Core Data Services (CDS) views in SAP HANA. It provides a detailed explanation of how associations work and how they differ from joins.
After watching this video, you will learn:
- The concept of associations in CDS views. Associations are relationships between a source entity and a target entity. They are similar to joins, but they are “lazy” in nature, meaning they only form when needed. This is different from joins, which always form regardless of whether the data from the target entity is accessed or not.
- The types of associations: Adhoc Association and Exposed Association. Adhoc associations are used within the CDS view where they are defined, while exposed associations are defined in a CDS view but can be used in other CDS views or SQL statements.
- How to create an association in a CDS view. The video demonstrates how to define an association using the “association” keyword, specify the cardinality, and provide the on condition.
- How to access data from an association. The presenter shows how to use the dot notation to access fields from the target entity of an association. This is referred to as a “path expression”.
- The behavior of associations when data from the target entity is not accessed. If no fields from the target entity are accessed, no join is formed. This is demonstrated by showing the native SQL statement that is executed when the CDS view is activated.
- The behavior of associations when data from the target entity is accessed. If fields from the target entity are accessed, a join is formed. This is also demonstrated by showing the native SQL statement that is executed when the CDS view is activated.
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