QR Codes for Unique Surveys

Here's the project:

We want to create surveys for customers to take (using a QR code) that are unique to an individual employee. For example, I go to an office. I get helped by Clerk A. I scan a QR code at Clerk A's workstation that takes me to the survey. The survey embeds that Clerk A helped me, without me entering in that information.

What would be the best way to go about doing this? How can I embed a Clerk ID into the survey without asking the respondent or creating unique surveys?

There are about 200 clerks, so I really don't want to make 200 separate surveys.