Counting How ID has Same Join Combination?

I has Join table, and result is like this

IDA IDB QTY
A   3   1
A   4   1
A   5   1
B   3   1
B   4   1
C   3   2
D   3   2
E   3   1
F   4   1
G   3   1
G   4   1
G   5   1
H   3   3
H   4   3
H   5   3

i’m confused how to count the IDA who has same Condition of IDB and QTY together.

So what i want is:

Combination of IDB - QTY 

(3-1, 4-1, 5-1) = 2 from IDA (A and G)
(3-1) = 1 from IDA (E) 
(3-2) = 2 from IDA (C and D) 

So basically i want count of IDA who has same IDB and QTY Combination. What Query should i do? i still don’t get how making query for this logic, thank you.

Edit :

What i want is the result in one query, i will not making manually Where condition of IDB-QTY Combination. (so basically the result is not from Where condition)

Answer

You can use aggregating with using group_concat() function

select group_concat( ida order by ida ) as grouped_letters, count(*) as count
  from
  (
   select ida, count( idb - qty ) as ct, sum( idb - qty ) as sm
     from tab
    group by ida
  ) q
 group by ct, sm
 order by ida;


+---------------+-----+
|grouped_letters|count|
+---------------+-----+
| B             |  1  | 
| C,D           |  2  |
| E             |  1  |
| F             |  1  |
| A,G           |  2  |
| H             |  1  |
+---------------+-----+

Demo