group_concat on numeric in MYsql

What is the problem? If you have a table like this:

table
id     description     qty
1      a                1
2      b                2
3      a                3
4      b                4

and you used a query like this

SELECT description, Group_Concat(qty) FROM table WHERE description = a;

then you would get these results

a 1,3

You should provide more info so we can help you more specifically.