What does it mean when a field type must be the same for joining datasets?

When a field type must be the same for joining datasets, it indicates that both fields involved in the join operation need to be designed to store the same data type. This is critical because a join operation typically combines records from two datasets based on matching values in specified fields. If the types of the fields do not match—such as one being a string and the other being an integer—the system will not be able to correctly align and connect the data from these datasets, leading to errors or exclusion of data from the output.

Ensuring that both fields share the same data type guarantees that the join can proceed without issues, allowing for accurate and meaningful results. This requirement fosters data integrity and consistency across the datasets being analyzed.