Using phpMyAdmin to update customer discount group assigments

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"?

I would advise creating a sql query to make your required changes. In MyPHPAdmin if you select your table there is an import tab, but I'd research this before using it. It may duplicate records instead of updating them. Your best bet is an update query for example

Update Customers
Set customers.customers_group_pricing = 2
Where customers.customers_group_pricing = 1

That is just a rough example but it might give you a direction to look in.

Thanks for the suggestion! I had thought of that already, however the problem is that we are breaking the customers out into all different groups to make it a bit more refined, so it pretty much has to be done manually, and the easiest way is by downloading the .csv files and working with them.

That is why I am trying to figure out how to import a file and just have it overwrite the existing data.