How To Fix MC731 - Required field &-& is not a key field

MC731 - Overview

• Message type: E = Error

• Message class: MC - Aggregate: views, matchcodes, lock objects

• Message number: 731

• Message text: Required field &-& is not a key field

What causes this issue?

Certain key fields of the primary and secondary tables must be included
as key fields of the view in order to ensure an unambiguous key for the
view.
The specified field is contained in the view but was not marked as a
key field.
For fields which are linked with a join, the field of a secondary table
which is connected with the key field of the primary table can be
included in the view instead of the key field of the primary table
itself. However, this means that this field will not be marked as a key
field, causing this message.

System Response

The view is activated. Errors can occur during maintenance with
transaction SM30.

How to fix this error?

We recommend that you keep the key fields suggested by the system
in the view.

Error message extract from SAP system. Copyright SAP SE.

MC731 - Details

• The SAP error message MC731, which states "Required field &-& is not a key field," typically occurs in the context of data entry or configuration in the SAP system, particularly in the area of Material Management (MM) or Logistics. This error indicates that a required field is not defined as a key field in the relevant table or structure, which is necessary for the operation you are trying to perform.
  
  Cause:
  
  Missing Key Field: The field that is required for the operation is not defined as a key field in the database table or structure.
  
  Configuration Issues: There may be issues in the configuration of the material master, info records, or other related master data.
  Data Entry Errors: The user may be trying to enter data in a way that does not comply with the expected structure or requirements of the system.
  
  
  Solution:
  
  Check Configuration: Review the configuration settings for the relevant master data (e.g., material