How To Fix DI756 - Field &-& may only be checked against key fields

SAP Error Message - Details

• Message type: E = Error

• Message class: DI - Dictionary messages: Indexes

• Message number: 756

• Message text: Field &-& may only be checked against key fields

What causes this issue?

Every secondary table of a lock object must be connected to a base
table above it in the hierarchy by a join condition. This join
condition must be implemented by a foreign key. This foreign key must
have the secondary table as foreign key table and the base table above
it in the hierarchy as check table. One of the join conditions of the
lock object is implemented via an inconsistent foreign key relationship.

System Response

The action is cancelled.

How to fix this error?

Ensure that the join condition is implemented via a valid foreign key
relationship.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message DI756 - Field &-& may only be checked against key fields ?

  The SAP error message DI756 indicates that a field in a data structure is being checked against a non-key field, which is not allowed in certain contexts, particularly when working with database tables or data elements that require key fields for validation.
  Cause:
  The error typically arises in the following scenarios:
  
  Incorrect Field Usage: You are trying to use a non-key field in a condition where only key fields are permitted. This often happens in ABAP programs, function modules, or when defining selection criteria in queries.
  Data Dictionary Issues: The field being referenced may not be defined as a key field in the relevant database table or structure.
  Logical Errors in Code: There may be a logical error in the code where the wrong field is being referenced for a check or comparison.
  
  Solution:
  To resolve the DI756 error, you can take the following steps:
  
  
  Check Field Definitions: Verify the definitions of the fields in the data dictionary (SE11). Ensure that the field you are trying to check is indeed a key field in the relevant table or structure.
  
  
  Modify the Code: If you are using a non-key field in your code, modify the logic to use a key field instead. This may involve changing the field in your SELECT statement, WHERE clause, or any other condition where the error is triggered.
  
  
  Review Data Model: If the field should logically be a key field, consider modifying the data model to include it as a key field. This requires careful consideration and may involve changes to the database structure.
  
  
  Debugging: Use the ABAP debugger to trace the execution of your program and identify where the error is occurring. This can help you pinpoint the exact line of code that is causing the issue.
  
  
  Consult Documentation: Review SAP documentation or community forums for additional context on the error and potential solutions.
  
  
  Related Information:
  
  Transaction Codes: You may need to use transaction codes like SE11 (Data Dictionary), SE80 (Object Navigator), or SE37 (Function Module) to investigate the definitions and usage of the fields.
  SAP Notes: Check for any relevant SAP Notes that might address this specific error or provide additional guidance.
  Community Forums: SAP Community and other forums can be valuable resources for finding similar issues faced by other users and their solutions.
  
  By following these steps, you should be able to identify the cause of the DI756 error and implement a suitable solution.