Which tool is best for combining data streams vertically by stacking them based on column name, position, or manually?

The Union Tool is designed specifically for combining data streams vertically, which means it stacks datasets one on top of another. It achieves this by aligning the columns based on names, their positions in the datasets, or through a manual specification by the user. This capability allows for seamless integration of similar datasets, making it particularly useful when you have multiple inputs with the same or similar structure and want to consolidate them into a single output.

On the other hand, the Join Tool is more focused on merging data sets based on specific matching criteria in shared fields, which is a horizontal combination rather than vertical. The Append Fields Tool is used to add columns from one dataset to another dataset which requires a row-wise arrangement, not a stacking of rows. Lastly, the Sort Tool is concerned with ordering rows within a dataset and does not combine or stack datasets at all. Thus, the Union Tool is the most suitable choice for the described task of vertical data combination.