Query n# of Records

Question

Creating a c# program founded on MS-SQL:

It is a medical program and patients are sometimes prescribed drugs, sometimes 1 prescription, sometimes 4, who knows.  I want the program user to be able to click a button and see the last prescription (possibly to scroll through all previous prescriptions) and  see what drugs were prescribed last.  Then another button and they can re-prescribe the same meds.  

I have a table with Patient Info and a prescription table that has Patient #, Visit #, and then drug info

How would i do a Query that pulls all the records of a particular patient, and then groups them by the Visit #.  

My initial thought is query all the pharmacy records of a patient and then do a foreach loop through that data.  but how would I group the data.  How do i have it find and group the unique VisitID numbers?

Pictures:

ID   PatID     VisitID    MedID

1        58         334          200

2        58         567          301

3        58         567          687

4        58         567          420

5        58         891          301

6        58         891          82

7        58         891          612

and I want to get 3 Groups of data (334, 567, 891) with (1,3,3) results respectively.  

Thank you