How To Fix RSRTS_CDS171 - Alias &1: nested CASE expressions are not supported

SAP Error Message - Details

• Message type: E = Error

• Message class: RSRTS_CDS - Messages Transient CDS Queries

• Message number: 171

• Message text: Alias &1: nested CASE expressions are not supported

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message RSRTS_CDS171 - Alias &1: nested CASE expressions are not supported ?

  The SAP error message RSRTS_CDS171 indicates that there is an issue with the use of nested CASE expressions in a Core Data Services (CDS) view or query. This error typically arises when you are trying to create a calculated field using a CASE statement that contains another CASE statement within it, which is not supported in the context of the query you are executing.
  Cause:
  The primary cause of this error is the use of nested CASE expressions in your CDS view or SQL query. SAP's CDS framework has certain limitations, and one of them is that it does not support nested CASE statements. This can happen if you are trying to implement complex logic that requires multiple layers of conditional statements.
  Solution:
  To resolve this error, you can consider the following approaches:
  
  
  Flatten the Logic: Instead of using nested CASE statements, try to flatten your logic into a single CASE statement. This may involve combining conditions or restructuring your logic to avoid nesting.
  Example:
  Instead of:
  CASE 
      WHEN condition1 THEN 
          CASE 
              WHEN condition2 THEN result1 
              ELSE result2 
          END
      ELSE result3 
  END
  You can try to combine the conditions:
  CASE 
      WHEN condition1 AND condition2 THEN result1 
      WHEN condition1 AND NOT condition2 THEN result2 
      ELSE result3 
  END
  
  
  Use Additional Calculated Fields: If the logic is too complex to flatten, consider breaking it down into multiple calculated fields. Create intermediate fields that handle parts of the logic separately, and then use those fields in your final calculation.
  
  
  Refactor the Query: If possible, refactor your query to avoid the need for nested CASE statements. This might involve changing how you retrieve or process your data.
  
  
  Check Documentation: Review the SAP documentation for any updates or best practices regarding the use of CASE statements in CDS views. There may be specific guidelines or examples that can help you structure your logic correctly.
  
  
  Related Information:
  
  SAP Notes: Check for any relevant SAP Notes that might address this specific error or provide additional context on limitations with CDS views.
  CDS View Documentation: Familiarize yourself with the official SAP documentation on Core Data Services, especially sections related to expressions and calculations.
  Community Forums: Engage with the SAP community forums or SAP Help Portal for discussions related to similar issues. Other users may have encountered the same problem and can offer insights or solutions.
  
  By following these steps, you should be able to resolve the RSRTS_CDS171 error and successfully execute your query without encountering nested CASE expression issues.