I use this query to get a value for a range of months. For example, January 1.10, February 2.37.
"SELECT SUM(DISTRIBUTED_AMOUNT / EXCHANGE_RATE)
FROM royalties
WHERE DATE BETWEEN '".$datemin."' AND '".$datemax."'
GROUP BY DATE
ORDER BY DATE ASC"
Is there a way to return a value of 0 if there are no rows within a certain month?