Ok this is going to sound like a very stupid question, but I'm very eerie about playing around in the databases since I don't always know exactly what I'm doing.

I need to do a mass change to about 1/2 my customers groups. I decided it would be best to download the CSV of the customers table and make the changes there under the column customers_group_pricing.

Here is my question, how do I upload the file?

Do I make the changes to the required customers, but upload the entire file again including the customers I didn't make any changes to, only checking off the option "Replace table data with file"?