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

MC801 - Overview

• 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

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MC801 - Details

• 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