In Data Flow, the source file will be transformed to get the expected values. When new values are generated, the existing file is updated directly with latest data.

To achieve this, it is required to use the same dataset in both source and sink transformations, this will result in overwriting the existing file with new values and gets updated during each execution.

Follow the below steps to achieve the situation:

Source Data:

Source Dataset in Data Flow Text Delimited:

For Sink we need to use the source dataset of dataflow:

In Sink settings , we need to keep the following configuration:
File name option: Output to single file
Output to single file : source_file_name

Output: Updated data in existing file