How to ORDER like my example?

[paradisehit]

 
 I use GROUP can manage the data that has the same "value" into one bag.
For example:
   character, num
    (b, 1)             (a, 1)
    (b, 2)  group (a, {(a, 2)})
   {(a, 1)}   => {     (a, 1)   }
    (a, 2)        (b, {(b, 1)})
    (a, 1)             (b, 2)
But now I wanna the result is orderd by the num, and also the same character is 
together.

just like this result:
 (b, 1)

 (b, 2)
 (a, 1)
 (a, 1)
 (a, 2)

and the alpha order is not changed.

How? Can someone help me?