How To Fix AQ500 - Only one link can be an outer join

SAP Error Message - Details

• Message type: E = Error

• Message class: AQ - Message texts for SAP Query

• Message number: 500

• Message text: Only one link can be an outer join

What causes this issue?

If more than two tables are involved in a table join, you can create a
link with a left outer or a right outer join only once.

System Response

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

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message AQ500 - Only one link can be an outer join ?

  The SAP error message AQ500, which states "Only one link can be an outer join," typically occurs in the context of SQL queries or when working with database views in SAP. This error indicates that the query or view definition is attempting to use multiple outer joins, which is not allowed in certain contexts.
  Cause:
  The error arises when:
  
  You are trying to create a SQL query or a view that includes more than one outer join (LEFT JOIN or RIGHT JOIN) in a single query.
  The database system or the specific SQL dialect being used does not support multiple outer joins in the same query.
  
  Solution:
  To resolve the AQ500 error, you can consider the following approaches:
  
  
  Review the Query Structure:
  
  Check the SQL query or view definition to identify where multiple outer joins are being used.
  Ensure that only one outer join is present in the query.
  
  
  
  Use Subqueries:
  
  If you need to include multiple outer joins, consider breaking the query into smaller parts using subqueries. You can first perform the outer join in a subquery and then join the result with other tables.
  
  
  
  Change Join Types:
  
  If possible, change the outer join to an inner join for one of the relationships, if the business logic allows it.
  
  
  
  Combine Results:
  
  If you need data from multiple tables, consider using UNION or UNION ALL to combine results from separate queries instead of trying to join them all in one query.
  
  
  
  Check Database Documentation:
  
  Refer to the documentation of the specific database you are using (e.g., HANA, Oracle, SQL Server) to understand its limitations regarding outer joins.
  
  
  
  Related Information:
  
  SQL Joins: Understanding the different types of joins (INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN) and their implications on data retrieval can help in structuring queries effectively.
  Performance Considerations: Be mindful of performance implications when restructuring queries, as subqueries and multiple joins can impact execution time.
  SAP Notes: Check SAP Notes and Knowledge Base Articles for any specific guidance or patches related to this error, as there may be updates or best practices provided by SAP.
  
  By following these steps, you should be able to resolve the AQ500 error and successfully execute your SQL query or view definition.