Key Definitions of &1 and &2 are different, &3 is missing in key of &1

What causes this issue?

The explicit defined key of the view &V1& is different than the key of
the underlying data source.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Adjust the key definition of the view by adding the key word KEY at the
appropriated elements.
This warning can be suppressed by putting the pseudo comment
/*+[hideWarning] { "IDS" : [ "KEY_CHECK" ] }*/
in front of the view definition.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.