I've gotten a large spreadsheet with patient IDs and dates of surgery. One column is patient ID (formatted as YYYYMMDDXXXX), another column is date of surgery (formatted as YYYY-MM-DD). The same patient could have had multiple surgeries, and thus be entered in the sheet multiple times but with different dates of surgery. What I want to do is find true duplicate entries, that is duplicates of both patient ID and date of surgery. How do I do this?

Basically all dates of surgery have duplicates since there are no days with jus a single surgery. And many patients have had multiple surgeries (revision surgeries etc), so many patient IDs are duplicate. But I have no idea how to relly pair those up?