I'm trying to concatenate the values Bs of a column depending on the value A of another column all this while counting the ocurrences of said value A, finally the selection of value A depends on the result of a CASE clause of column C and D

If i have this table
| COLUMN_A | COLUMN_B | COLUMN_C | COLUMN D |
| ------------ | ------------ | ------------ | ------------ |
| NAME1 | A | 10 | 8 |
| NAME2 | B | 20 | 15 |
| NAME1 | C | 15 | 10 |
| NAME4 | D | 23 | 20 |
| NAME3 | E | 40 | 43 |
| NAME2 | F | 10 | 14 |
| NAME5 | G | 12 | 20 |

I want to select only those of COLUMN A where COLUMN C values are greater than COLUMN D, count the times it happens and finally concatenate COLUMN B values (if apply), something like this :

I've managed to acomplish almost all of this with the next query

SELECT 
    CASE WHEN columnc > columnd THEN [columna] ELSE 'Doesnt apply' END as ResultA,
    STUFF((
        SELECT ',' + columnb as 'data()' 
        FROM sometable 
        WHERE (columna = sometable.columna)
        FOR XML PATH(''),TYPE).value('(./text())[1]','VARCHAR(MAX)'),1,2,'') AS ResultB,
    COUNT(*) AS count
FROM sometable 
GROUP BY 
    CASE WHEN columnc > columnd THEN [columna] ELSE 'Doesnt apply' END
HAVING COUNT(*) >= 1

But it bring all the COLUMN B values even those where COLUMN A value is not present.