SQL monthly join and monthly total percentage

Question

My head smokes from (stupid) attempts to use it JOIN, WITHand GROUP BYto come up with a solution for my fairly common scenario, I just can't wrap my head around me. Let me give you an example right away:

I have two tables (ColorCount and Colorname):

ColorCount:
ColorID Count Date
1       42    2010-09-07
1       1     2010-09-08
2       22    2010-09-14
1       20    2010-10-10
3       4     2010-10-14

---

ColorName:
ColorID  Name
1        Purple
2        Green
3        Yellow
4        Red

---

Now all I want to do is join the ColorName table in the ColorCount table, summarize all the color counts per month and calculate the percentage of each count of the total amount. Tables are better than words:

Output:
Month Color   Count Percentage
09    Purple  43    66%
09    Green   22    33%
09    Yellow  0     0%
09    Red     0     0%
10    Purple  20    83%
10    Green   0     0%
10    Yellow  4     16%
10    Red     0     0%

(Please note that the total number of months 09is equal 65, therefore 66%for Purple, as well as 0for non-existent colors):

I hope someone dreams in SQL, and this is not an easy task ...

Answer 1

:

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:

;with cte (ColorId, Mth, TotalCount)
 as (select
        ColorId
       ,dateadd(dd, -datepart(dd, Date) + 1, Date) Mth
       ,sum(Count) TotalCount
      from ColorCount
      group by ColorId, dateadd(dd, -datepart(dd, Date) + 1, Date))
 select
    AllMonths.Mth [Month]
   ,cn.Name
   ,isnull(AggData.TotalCount, 0) [Count]
   ,isnull(100 * AggData.TotalCount / sum(AggData.TotalCount * 1.00) over (partition by AllMonths.Mth), 0) Percentage
  from (select distinct Mth from cte) AllMonths
   cross join ColorName cn
   left outer join cte AggData
    on AggData.ColorId = cn.ColorId
     and AggData.Mth = AllMonths.Mth
  order by AllMonths.Mth, cn.ColorId

Answer 2

SELECT
    [Month],
    [Name],
    [Count],
    CASE WHEN TotalMonth=0 THEN 'INF' ELSE cast(round([Count],0)*100.0/TotalMonth,0) as int) + '%' END as [Percentage]
FROM 
(
SELECT 
    [Months].[Month] as [Month],
    CN.[Name],
    isnull(CC.[Count],0) as [Count],
    (SELECT SUM([Count]) FROM ColorCount WHERE 
            datepart(month,[Date])=datepart(month,CC.[Date])
     ) as [TotalMonth]
FROM (SELECT DISTINCT datepart(month,[Date]) as [Month] FROM ColorCount) [Months]
LEFT JOIN ColorName CN ON [Months].[Month]=datepart(month,CC.[Date])
LEFT JOIN ColorCount CC ON CN.ColorID=CC.ColorID
) AS tbl1
ORDER BY
    [Month] ASC,
    [Name] ASC

- .... , ?