How To Fix MC755 - Joins must be defined with foreign key

SAP Error Message - Details

• Message type: E = Error

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

• Message number: 755

• Message text: Joins must be defined with foreign key

What causes this issue?

Join conditions were freely defined for a view. The current view type,
however, only permits joins which were defined with foreign key.
Tables containing no join conditions are also not allowed.

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

System Response

How to fix this error?

Normally the ABAP/4 Dictionary only permits the entry of freely defined
join conditions for database views. The current situation occurred due
to the change in the view type.
Choose the base tables with a foreign key relationship for all views
except for database views. The foreign key relationship is then used as
the join definition.
&NOTE&
The information that the join might have been derived from a
foreign key is not stored for database views. In this case you should
remove all the tables except for one. Use the 'Relationships' function
to include the tables after successfully converting the view type.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message MC755 - Joins must be defined with foreign key ?

  The SAP error message MC755 ("Joins must be defined with foreign key") typically occurs in the context of SAP's data modeling or reporting tools, such as SAP BW (Business Warehouse) or SAP HANA. This error indicates that a join operation between two tables is being attempted without a defined foreign key relationship, which is necessary for the system to understand how the tables are related.
  Cause:
  
  Missing Foreign Key: The primary cause of this error is that the tables you are trying to join do not have a defined foreign key relationship in the data model. Foreign keys are essential for ensuring data integrity and establishing relationships between tables.
  Incorrect Data Model Configuration: The data model may not be properly configured to reflect the relationships between the entities involved.
  Incompatible Data Types: The fields being joined may have incompatible data types, which can also lead to issues when trying to establish a join.
  
  Solution:
  
  
  Define Foreign Keys:
  
  Go to the data model where the tables are defined.
  Identify the tables involved in the join operation.
  Define a foreign key relationship between the relevant fields in the tables. This can usually be done in the data modeling tool by selecting the appropriate fields and specifying the relationship.
  
  
  
  Check Data Model Configuration:
  
  Review the overall data model to ensure that all necessary relationships are defined.
  Ensure that the join conditions are correctly set up in the data model.
  
  
  
  Verify Data Types:
  
  Check the data types of the fields you are trying to join. Ensure that they are compatible (e.g., both should be of the same type, such as integer, string, etc.).
  If necessary, convert the data types to ensure compatibility.
  
  
  
  Rebuild the Query:
  
  If the issue persists, consider rebuilding the query or the data model to ensure that all relationships are correctly established.
  
  
  
  Consult Documentation:
  
  Refer to SAP documentation or help resources for specific instructions on defining foreign keys and setting up joins in the context of your specific SAP environment.
  
  
  
  Related Information:
  
  SAP Notes: Check for any relevant SAP Notes that may address this specific error or provide additional guidance.
  SAP Community: Engage with the SAP Community forums to see if other users have encountered similar issues and what solutions they have found.
  Training and Tutorials: Consider looking for training materials or tutorials on data modeling in SAP BW or SAP HANA, which can provide deeper insights into best practices for defining relationships and joins.
  
  By following these steps, you should be able to resolve the MC755 error and successfully define the necessary joins in your SAP environment.