How To Fix DDLS328 - select * and $extension can cause duplicate fields

SAP Error Message - Details

• Message type: E = Error

• Message class: DDLS - For DDL source handling

• Message number: 328

• Message text: select * and $extension can cause duplicate fields

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message DDLS328 - select * and $extension can cause duplicate fields ?

  The SAP error message DDLS328 indicates that there is a potential issue with the use of SELECT * in conjunction with $extension in a data definition language (DDL) context. This error typically arises when there are duplicate fields in the result set due to the way the database is structured or how the query is constructed.
  Cause:
  
  Duplicate Fields: The use of SELECT * retrieves all fields from the specified tables or views. If there are fields with the same name in the main table and in the $extension (which is often used for extending the data model), this can lead to ambiguity and duplication in the result set.
  Data Model Design: The underlying data model may have been designed in such a way that it allows for overlapping field names, especially when extensions are involved.
  Inconsistent Naming Conventions: If the naming conventions for fields are not consistent, it can lead to situations where fields from different sources have the same name.
  
  Solution:
  
  *Avoid `SELECT **: Instead of usingSELECT *`, explicitly specify the fields you need in your query. This will help you avoid retrieving duplicate fields.
  SELECT field1, field2, field3 FROM your_table
  
  Use Aliases: If you must include fields that may have the same name, consider using aliases to differentiate them.
  SELECT main.field1 AS main_field1, ext.field1 AS ext_field1 FROM your_table AS main
  JOIN your_extension AS ext ON main.id = ext.id
  
  Review Data Model: Check the data model to ensure that field names are unique across tables and extensions. If necessary, refactor the model to avoid naming conflicts.
  Check for Extensions: If you are using extensions, review the fields defined in those extensions to ensure they do not conflict with the base table fields.
  
  Related Information:
  
  SAP Documentation: Refer to the official SAP documentation for guidelines on best practices for data modeling and SQL queries.
  Data Dictionary: Use the Data Dictionary (SE11) to analyze the structure of the tables and extensions involved in your query.
  Debugging Tools: Utilize debugging tools in SAP to trace the execution of your query and identify where the duplication occurs.
  
  By following these steps, you should be able to resolve the DDLS328 error and prevent it from occurring in the future.