A separate row for each one would be a good idea - in fact a separate table. That's the idea of a relational database - it stores relations between sets of data.
Your modules have ID numbers, and so no doubt do your categories. No doubt you have one table lists the modules as well as one that lists the categories.
The third table would just contain
category_id | module_id
------------+----------
1 | 1
2 | 1
2 | 2
3 | 7
1 | 4
2 | 10
3 | 1
2 | 3
3 | 3
1 | 3
1 | 8
3 | 2
using your example and some made-up category IDs.
