This will give you the overall top 5 users, not the top five users per code group. Given:

code userid count
1    corion 1000
2    corion 999
3    corion 888
4    corion 777
5    corion 6
1    moritz 555
2    moritz 444
3    moritz 333
4    moritz 222
5    moritz 1
[download]

ordering by count,code would never show moritz, and you'd always miss out on low-counting codes (like code 5). Ordering by code, count would leave out codes with very few users (if you have 1000 users of code 1 and only 3 of code 5).