generate empty rows even if empty between 2 dates

Question

I have this simple query that fetches all completed orders between 2 dates(about 6 months at a time):

select IFNULL(sum(o.amount), 0) as amount, o.completed_         


        

Answer 1

Try with coalesce function which will return '0' if the sum(orders.amount) is null for a specific month:

select COALESCE(sum(o.amount), 0) as amount, o.completed_at 
from orders o 
where date(o.completed_at) between '2011/10/01' and '2012/03/06' 
group by year(o.completed_at), month(o.completed_at) order by o.completed_at