Module 19: CDS Views – Fundamentals

Core Data Services (CDS) is SAP’s strategic data modeling layer on top of the database.
CDS is not just about performance — it defines what the data means, not just how it is selected.

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1. What is CDS?

Definition

CDS (Core Data Services) is a declarative data definition language used to define semantically rich data models directly on the database.

Why CDS Exists

Traditional Open SQL:

• Retrieves data
• Has no semantics
• Limited reuse

CDS:

• Defines data + meaning
• Enables code pushdown
• Reusable across ABAP, OData, analytics
• Authorization-aware

SAP Direction

In S/4HANA, CDS is the default data access layer.

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2. Where CDS Fits in the Architecture

Database (HANA) ↑ CDS Views (Semantic Layer) ↑ ABAP / OData / RAP / Analytics

Mental Model

Think of CDS as ABAP Dictionary + Open SQL + semantics combined.

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3. Basic CDS Syntax

A CDS view is defined using DDL Source in ADT (Eclipse).

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3.1 Basic CDS View Example

@AbapCatalog.sqlViewName: 'ZV_FLIGHT'
@EndUserText.label: 'Flight Data'
define view Z_CDS_Flight
  as select from spfli
{
  key carrid,
  key connid,
      cityfrom,
      cityto
}

Key Elements

• define view

• select from

• Field list

• Keys

Naming Convention

• CDS view name → Z_CDS_*

• SQL view name → 16 characters, uppercase

4. Annotations (Very Important)

Annotations add metadata and semantics to CDS views.

4.1 Common Annotations

@EndUserText.label: 'Airline'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK

Categories of Annotations

• UI annotations

• Analytics annotations

• Authorization annotations

• Catalog annotations

Why Annotations Matter

Annotations drive:

• Fiori UI behavior

• Analytics

• Authorization

• OData exposure

5. Associations vs Joins

5.1 Joins (Classic SQL Style)

define view Z_CDS_FlightJoin
  as select from spfli
  inner join scarr
    on spfli.carrid = scarr.carrid
{
  spfli.carrid,
  spfli.connid,
  scarr.carrname
}

5.2 Associations (CDS Way – Recommended)

define view Z_CDS_FlightAssoc
  as select from spfli
  association [0..1] to scarr as _Carrier
    on $projection.carrid = _Carrier.carrid
{
  key carrid,
  key connid,
      _Carrier.carrname
}

Why Associations Are Better

Aspect	Join	Association
Eager loading	Yes	No
Reuse	Low	High
Semantics	Low	High
Performance	OK	Better (lazy)

Golden Rule

Prefer associations over joins unless eager data is required.

6. Parameterized CDS Views

Parameterized CDS views accept input parameters.

Example

define view Z_CDS_Flight_Param
  with parameters
    p_carrid : spfli.carrid
  as select from spfli
{
  key carrid,
  key connid,
      cityfrom,
      cityto
}
where carrid = :p_carrid

Usage in ABAP:

SELECT * FROM Z_CDS_Flight_Param( p_carrid = @lv_carrid )
  INTO TABLE @DATA(lt_flights).

Use Case

Parameterized CDS replaces many dynamic WHERE conditions.

7. CDS vs Open SQL (When to Use What)

Scenario	Recommendation
Reusable data model	CDS
Analytics / Reporting	CDS
One-off simple SELECT	Open SQL
OData / RAP	CDS
Complex DB logic	CDS / AMDP

8. Common Beginner Mistakes

Avoid These

• Treating CDS like a simple SELECT

• Overusing joins instead of associations

• Missing authorization annotations

• Hard-coding logic better suited for CDS

• Creating very large monolithic CDS views

9. Summary

• CDS is SAP’s semantic data model

• Defined using DDL in Eclipse

• Annotations add meaning and behavior

• Associations are preferred over joins

• Parameterized CDS adds flexibility

• CDS is reusable across layers

10. Practice Exercises

• Create a basic CDS view on a database table.

• Add meaningful annotations.

• Replace a JOIN with an association.

• Create a parameterized CDS view.

• Consume CDS view in ABAP SELECT.

11. What’s Next?

➡️ Module 20: Advanced CDS Views

Learning Tip

If you understand CDS fundamentals well, RAP and analytics become much easier.