Group by "Datum" Problem

[mkinzler]

Versuch es mal mit einer Derived Table:

SQL-Code:

SELECT
    s.monat,
    Sum(s.snh_dosenmenge) as dosenmenge 
from
    (
        select     
            EXTRACT (MONTH FROM snh_datum) AS monat,
            EXTRACT (YEAR FROM snh_datum) as jahr
            snh_dosenmenge
        FROM 
            snack_haupt) s
WHERE 
    s.jahr = :year
GROUP BY 
    monat
ORDER BY 
    Monat DESC;