What's the default configuration of the union tool?

The default configuration of the union tool in Alteryx is to join by column name. This means that when you use the union tool to combine multiple data streams, it automatically looks for columns with matching names in each data source. If these names are the same, the tool aligns the data based on those names, which facilitates a seamless integration of the data into a single output.

By joining based on column name, this method ensures that the data from different sources is matched correctly and helps maintain data integrity. It is especially useful in scenarios where you are pulling in datasets from different origins that might have identical column structures. If column names do not match, those fields will still be included in the output but will be represented with nulls in columns without corresponding data.

In contrast, the other choices focus on different joining criteria that are not the default behavior of the union tool. For instance, joining by column index or data type could lead to mismatched data if the structures of the datasets vary, and joining by unique value is not applicable in a union context since unions are meant to concatenate datasets rather than merge based on unique matching keys.