[ABAP] OpenSQL: Aggregatfunktionen

* DEMO_SQL_EXPR_IN_AGGREGATES

* Funktionen:
*   AVG
*   MAX
*   MIN
*   MEDIAN
*   SUM
*   CORR
*   COUNT
*   GROUPING

Links

• https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abensql_agg_func.htm
• https://discoveringabap.com/2021/12/12/abap-7-4-and-beyond-12-abap-sql-aggregate-queries-and-for-all-entries/
• https://github.com/SAP-samples/abap-cheat-sheets/blob/main/03_ABAP_SQL.md