You can not use APPEND to add an element to a table with a unique key defined, like a hashed table or a standard table with a unique key — because APPEND simply adds a new row at the end without checking keys.
If you try APPEND. This will add the row without checking the key. This can lead to duplicates and the ABAP runtime won’t raise an error, but your table integrity could be compromised.
If you want to update if exists, or insert if not.
Added small code snippet .
