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

in this article, we will explore how the update 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 update data action the update data action determines whether a record in the selection results is new or existing for new records, deselect segment adds them to the end of the target data extension for existing records, the system updates the record with the result data this action requires the use of a primary key, which serves as a reference to check record existence here's an 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 english c 103 maria juarez mariajuarez\@outlook com spanish sample selection results customer id first name last name email language c 100 jane jones jjones1955\@hotmail com french c 102 paul chang paul chang2\@yahoo com chinese c 112 bjorn svenson b svenson\@yahoo com swedish c 104 marie benoit m benoit\@gmail com french after running the selection, the updated target data extension will contain the following data (with primary key customer id) the final data in the target data extension will be sorted by primary key and the existing records (in italics) will be updated with the data from the selection results customer id \[pk] first name last name email language c 100 jane jones jjones1955\@hotmail com french c 101 kofi abimbola kofi1234\@gmail com dutch c 102 paul chang paul chang2\@yahoo com chinese c 103 maria juarez mariajuarez\@outlook com spanish c 112 bjorn svenson b svenson\@yahoo com swedish c 104 marie benoit m benoit\@gmail com french 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