在知道您有日历表之前，我已经做完了。我已经习惯master.dbo.spt_values了连续十二个月（包括当前）。
declare @ProductNo int
set @ProductNo = 1234
select MONTH(d.date), YEAR(d.date), isnull(t.amnt, 0) as [Units sold] from (
SELECT
YEAR(o.OrderDate) as 'Year',
MONTH(o.OrderDate) as 'Month',
sum(Amount) as amnt,
[ProductNo]
FROM [OrderLine] ol
inner join [Order] o on ol.OrderNo = o.OrderNo
where ProductNo = @ProductNo
group by ProductNo, YEAR(o.OrderDate), Month(o.OrderDate)
) t
right join (
select dateadd(mm, -number, getdate()) as date
from master.dbo.spt_values
where type = 'p' and number < 12
) d on year(d.date) = t.[year] and month(d.date) = t.[month]
order by YEAR(d.date), MONTH(d.date)
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