Before loading a table, it's necessary to transform it first to ensure its cleanliness. When merging two columns into one, there are several options to choose from. Once you've selected the two columns you want to merge, you can click 'Transform. Then, in the 'Merge Column' menu, you can choose how you want to merge the selected columns.
In addition to this option, you can also go to 'Add Column,' and a 'Merge Column' function will appear for you. For instance, if you want to add a comma between two columns to connect two tables, you need to be aware that if you perform a merge using the 'Transform' method, a comma might appear at the end. However, this issue doesn't occur if we use the 'Merge Column' from the 'Add Column' option."