How To Fix MC801 - View &-& can only be used in union & if a join with & exists

SAP Error Message - Details

• Message type: E = Error

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

• Message number: 801

• Message text: View &-& can only be used in union & if a join with & exists

Self-Explanatory Message

Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.

To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.

Unfortunately, there isn't any extra information in this error notice.

What else can you do?

First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).

Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.

You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.

Smart SAP Assistant

• What is the cause and solution for SAP error message MC801 - View &-& can only be used in union & if a join with & exists ?

  The SAP error message MC801 typically occurs in the context of SAP BW (Business Warehouse) or SAP HANA when you are trying to create or execute a query that involves a view or a join that is not properly defined or is incompatible with the existing data model.
  Cause:
  The error message "MC801 View &-& can only be used in union & if a join with & exists" indicates that there is an issue with how the views or joins are structured in your query. Specifically, it suggests that:
  
  Incompatible Joins: You are trying to use a view in a way that is not allowed because it requires a specific join condition that is not met.
  Union Requirement: The view can only be used in a union operation if a join with another specified view or table exists.
  Data Model Issues: There may be issues with the underlying data model, such as missing relationships or incorrect definitions of the views.
  
  Solution:
  To resolve this error, you can take the following steps:
  
  
  Check View Definitions: Review the definitions of the views involved in your query. Ensure that they are correctly defined and that the necessary joins are established.
  
  
  Review Joins: Ensure that the joins between the views or tables are correctly set up. If you are using a union, make sure that the views you are trying to union have compatible structures.
  
  
  Modify Query: If the query is attempting to use a view in a way that is not allowed, consider restructuring the query. You may need to break it down into smaller parts or use different views that are compatible.
  
  
  Consult Documentation: Refer to SAP documentation or help resources for specific guidelines on how to structure queries involving views and joins.
  
  
  Test in Isolation: If possible, test the views and joins in isolation to identify where the issue lies. This can help you pinpoint the exact cause of the error.
  
  
  Seek Help from SAP Support: If you are unable to resolve the issue, consider reaching out to SAP support or consulting with a colleague who has experience with SAP BW or HANA.
  
  
  Related Information:
  
  SAP BW Documentation: Look for specific documentation related to query design and view management in SAP BW.
  SAP Community: Engage with the SAP Community forums where other users may have encountered similar issues and can provide insights or solutions.
  Training Resources: Consider taking training courses on SAP BW or HANA to better understand how to work with views and joins effectively.
  
  By following these steps, you should be able to identify and resolve the cause of the MC801 error in your SAP environment.