SAP CDS ASSOC JOIN V1 ABEXA

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ABAP_CDS_DDL - DDIC-Based View, Joins of Associations
This example demonstrates how path expressions are transformed to joins in ABAP CDS.

ABAP_SOURCE_CODE
DEMO CL_DEMO_CDS_ASSOC_JOINS

ABAP_DESCRIPTION
This example demonstrates which joins are implemented for path expressions containing CDS associations. The following two CDS views - DEMO_CDS_ASSOC_JOIN1_O and DEMO_CDS_ASSOC_JOIN1_I - access their own association _demo_join2 in path expressions of the SELECT list and the exposed CDS association _demo_join3 of DEMO_CDS_ASSOC_JOIN2.
DDLS DEMO_CDS_ASSOC_JOIN1_O
DDLS DEMO_CDS_ASSOC_JOIN1_I
DDLS DEMO_CDS_ASSOC_JOIN2
LEFT OUTER and INNER are explicitly specified in the path expressions.

LEFT OUTER specifies the implementation of CDS associations as a left outer join, which is the default behavior at these places.

INNER specifies the implementation of CDS associations as an inner join, which overwrites the default behavior at these places.
In the DDL source code editor of the ADT, the respective join can be seen in the display of the generated SQL DDL statement.
This example shows that the result sets of the CDS views DEMO_CDS_ASSOC_JOIN1_O and DEMO_CDS_ASSOC_JOIN1_I are identical to the result sets of AB-SQL statements SELECT with explicitly programmed left outer and inner joins. The CDS views and the DDIC database table DEMO_JOIN3 above are accessed. All involved database tables are filled with sample data. With an inner join, unlike a left outer join, only the row is returned for which the join condition t3~l = t2~d is fulfilled.