How does the Append Data Action work in the Output Step?

in this article, we will explore how the append data action works for a target data extension with the help of some sample data when utilizing deselect segment to store selection results in target data extensions, you have three key data actions at your disposal overwrite, append, and update in this article, we will delve into the append data action, its functionality, and how it impacts your target data extensions within sfmc understanding these data actions will help you effectively manage and manipulate data to optimize your marketing campaigns append data action the append data action adds new records to the existing ones in the target data extension if no primary key is specified, the new results are appended after the existing records, potentially leading to duplicates however, when a primary key is defined, it's crucial to apply prio deduplication to avoid https //support deselect com/hc/en us/articles/360018237418 consider the following example before running the selection, let's assume the target data extension contains the following data customer id first name last name email language c 100 jane jones jjones1955\@hotmail com english c 101 kofi abimbola kofi1234\@gmail com dutch c 102 paul chang paul chang\@yahoo com chinese c 103 maria juarez mariajuarez\@outlook com spanish sample selection results customer id first name last name email language c 102 paul chang paul chang\@yahoo com chinese c 104 marie benoit m benoit\@gmail com french c 112 bjorn svenson b svenson\@yahoo com swedish c 100 jane jones jjones1955\@hotmail com english c 102 paul chang paul chang2\@yahoo com english if there’s no primary key (pk) set, after running the selection, the updated target data extension will contain the following data the data in the target data extension will contain the previously existing data (in italics) with the new results added after the last record of the existing data the order of the newly added records will be the same as how the resulting records were generated customer id first name last name email language c 100 jane jones jjones1955\@hotmail com english c 101 kofi abimbola kofi1234\@gmail com dutch c 102 paul chang paul chang\@yahoo com chinese c 103 maria juarez mariajuarez\@outlook com spanish c 102 paul chang paul chang\@yahoo com chinese c 104 marie benoit m benoit\@gmail com french c 112 bjorn svenson b svenson\@yahoo com swedish c 100 jane jones jjones1955\@hotmail com english c 102 paul chang paul chang2\@yahoo com english if there's a primary key set, after running the selection, the updated target data extension will contain the following data (with pk customer id and prio deduplication) the prio deduplication is set on customer id as the unique value (as that’s the primary key) and the field deciding which one to keep is “language = english” the final data in the target data extension (tde) will be in the order of the existing records ( in italics ) with new ones added at the end in addition, if a duplicate record meets the prio deduplication criteria, it will be handled the same as existing and new records ie if after prio dedup an existing record will be kept, then it will stay in its place in the final target data extension result if the de duplicated record kept is new, it will be added to the end of the tde so for example paul chang’s record with email paul chang2\@yahoo com is new and added to the end of the tde customer id \[pk] first name last name email language c 100 jane jones jjones1955\@hotmail com english c 101 kofi abimbola kofi1234\@gmail com dutch c 103 maria juarez mariajuarez\@outlook com spanish c 104 marie benoit m benoit\@gmail com french c 112 bjorn svenson b svenson\@yahoo com swedish c 102 paul chang paul chang2\@yahoo com english conclusion deselect segment offers powerful data actions—overwrite, append, and update—to manage target data extensions in sfmc efficiently understanding the behavior of each action helps ensure accurate and streamlined data operations within your marketing campaigns