This tutorial is an introduction to an Advance View Building with the Core Data Service in ABAP on SAP HANA based on SAP NetWeaver Application Server As ABAP 7.4.
Core Data Services
CDS (Core Data Services) is a collection of domain-specific languages and services which are used for defining and consuming semantically rich data models in SAP HANA
The Domain-specific languages are based on Entity-Relationship models such as
- Query Language
- Data Definition Language
- Expression Language
Integrating CDS in ABAP Server
Integrating CDS in ABAP servers simplifies related data models consumption by the means of 'view entitles' and also supports the code push down to the database layer.
Advantages of Integrating CDS in ABAP
- Semantically enriched data models can be defined in DDL Source object which is integrated with ABAP dictionary
- Code push down is supported through view building functionality which was not provided by open SQL.
- CDS gets fully integrated with ABAP structure
- Open SQL can be used on view entities which enable us to optimize applications based on open SQL.
Bottom-Up Approach
The currently optimize way for using HANA view in ABAP is called Bottom-Up approach.
In Bottom-Up approach first, the HANA views have to be developed in HANA server and then the External view is created in the ABAP server. HANA delivery unit and its corresponding HANA Transport-container ensure that HANA and ABAP content transported together.
This Bottom-UP approach involves the problem of having a different independent life cycle in TMS (Transport Management System) for the HANA and ABAP content.
Top-Down Approach
The new way of using HANA view in ABAP is Top-Down Approach with CDS view entities. The solution for the problem faced in Bottom-Up approach is provided by Top-Down Approach in CDS View. Developers are now able to create a managed whole life-cycle of HANA views in an ABAP Development Environment.
In this Top-Down Approach, the CDS view is defined in ABAP DDL source object and the corresponding HANA view is automatically created in the database during the CDS activation.
Advantage of Top-Down Approach
- The main benefit of this approach is that only the CDS view has to be transported by the Standard ABAP Transport CTS(Change & transport System).
- No HANA delivery or HANA transport system is required in this approach.
- Developers only need ABAP development tools for building and managing the CDS view. There is no need for additional HANA development tools.
Below is the DDL source object containing a sample view CDS View building where we can see the name of CDS View entity, the name of associated SQL view which is managed by ABAP dictionary and also some of the available features.
When to use CDL view instead of Open SQL
As we know an open SQL is the first tool for ABAP developers for pushing down the data for processing into database layer. Several improvements have been provided in this area with the latest SAP NetWeaver deliveries such as Aggregate functions, Conditional functions etc. But when it comes reuse of the data models or data features it is not available in Open SQL like Unions and associations then we can opt for CDS based advance view building.
How to access and preview an existing DDL source object
Go to CDS view definition and open DDL source file
We can preview DATA by going to Open Data Preview
Below is the image of data preview
