All fields are evaluated as key field

What causes this issue?

In the view, not all of the mandatory fields were included as key
fields. The key of the view therefore is not unique.

System Response

All the fields are regarded as key fields in order to guarantee that
the key lengths are unique.

How to fix this error?

For views with a large number of fields, this could have a negative
effect on the performance for the language construction described
below. In this case, all the mandatory key fields should be included in
the view.


&HINTS&
The key information is relevant for the ABAP/4 language constructs
SELECT SINGLE, SELECT ... ORDER BY PRIMARY KEY and SELECT ... FOR ALL
ENTRIES.
In these cases, SELECT SINGLE is handled like a simple SELECT ...
ENDSELECT, where the first (random) record found is returned.
ORDER BY PRIMARY KEY and (indirect) SELECT FOR ALL ENTRIES sort
according to all fields in these cases.

Error message extract from SAP system. Copyright SAP SE.