What happens if data types do not match during a join?

When data types do not match during a join operation, the behavior is such that no data will be joined. This is due to the fact that a successful join requires that the fields being matched between the datasets share the same data type. If one field is an integer and the other is a string, for example, the join won't find any matching values because the types are incompatible, preventing any rows from being combined. Consequently, the result of the join will effectively be an empty dataset, as there are no conditions met to perform the join based on mismatched data types.