How To Fix MC802 - Union &: number of columns is not correct

SAP Error Message - Details

• Message type: E = Error

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

• Message number: 802

• Message text: Union &: number of columns is not correct

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 MC802 - Union &: number of columns is not correct ?

  The SAP error message MC802, which states "Union &: number of columns is not correct," typically occurs in the context of SAP BW (Business Warehouse) or SAP BI (Business Intelligence) when there is an issue with the structure of a query or a data model that involves a union operation. This error indicates that the number of columns in the datasets being combined does not match, which is a requirement for union operations.
  Cause:
  
  
  Mismatched Column Count: The most common cause of this error is that the datasets being combined in the union operation have a different number of columns. For a union to work, all datasets must have the same number of columns and compatible data types.
  
  
  Incorrect Query Design: If you are designing a query that involves multiple InfoProviders or queries, the structure of these InfoProviders or queries may not align properly.
  
  
  Data Source Changes: If there have been changes to the underlying data sources (like InfoObjects or InfoProviders) that affect the number of columns or their structure, this can lead to the error.
  
  
  Transformation Issues: If you are using transformations to load data into a DataStore Object (DSO) or InfoCube, and the transformation logic is not correctly set up, it can lead to mismatched columns.
  
  
  Solution:
  
  
  Check Column Count: Review the datasets involved in the union operation. Ensure that they all have the same number of columns. If they do not, you will need to adjust the queries or data sources to ensure they match.
  
  
  Align Data Types: Ensure that the data types of the corresponding columns in each dataset are compatible. If necessary, use casting or conversion functions to align the data types.
  
  
  Review Query Design: If you are using a query that combines multiple InfoProviders, check the design of the query to ensure that all selected fields are consistent across the InfoProviders.
  
  
  Update Transformations: If the error is related to data loading, review the transformations to ensure that they are correctly mapping the fields and that the number of fields being loaded matches the target structure.
  
  
  Test with Sample Data: If possible, test the union operation with a smaller set of data to isolate the issue and confirm that the structure is correct.
  
  
  Consult Documentation: Refer to SAP documentation or community forums for specific guidance related to your version of SAP BW/BI, as there may be version-specific considerations.
  
  
  Related Information:
  
  SAP Notes: Check for any relevant SAP Notes that may address this specific error or provide additional troubleshooting steps.
  SAP Community: Engage with the SAP Community forums to see if other users have encountered similar issues and what solutions they found effective.
  Training and Documentation: Consider reviewing training materials or documentation related to query design and data modeling in SAP BW/BI to enhance your understanding of how unions work in this context.
  
  By following these steps, you should be able to identify and resolve the cause of the MC802 error in your SAP environment.