You can add new columns to an existing CSV to either:
- Add new rows with extra column(s)
- Updating all of the existing rows to include extra column(s)
Let's say we have a simple table called Users that has 2 columns: Id, and Name. We've started collecting users' zip codes, so we want to include a third column called Zip Code with the new rows we're adding.
From Settings > Data Sources, choose your CSV.
In the General tab, click Upload Alternate CSV Files.
We want to add new users with zip code data, so we're going to choose Append to existing table. If you want to add column values to existing rows, choose Replace an existing table. Select the table you want to update, and choose your CSV file from your local file system.
Next, we'll need to map our new columns to existing ones. For our new Zip Code column, we'll choose New Column from the dropdown and add a name (because our file didn't contain column headers).
Click Upload New Data, and you're all set!