Sql-server – Sum date between two date and group by month

This first query creates different Start Date and End Date ranges with no overlaps.

Note:

• Your sample(id=0) is mixed with a sample from Ypercube (id=1)
• This solution may not scale well with huge amount of data for each id or huge number of id. This has the advantage of not requiring a number table. With large dataset, a number table will very likely give better performances.

Query:

SELECT DISTINCT its.id
    , Start_Date = its.Start_Date 
    , End_Date = COALESCE(DATEADD(day, -1, itmax.End_Date), CASE WHEN itmin.Start_Date > its.End_Date THEN itmin.Start_Date ELSE its.End_Date END)
    --, x1=itmax.End_Date, x2=itmin.Start_Date, x3=its.End_Date
FROM @Items its
OUTER APPLY (
    SELECT Start_Date = MAX(End_Date) FROM @Items std
    WHERE std.Item_ID <> its.Item_ID AND std.Start_Date < its.Start_Date AND std.End_Date > its.Start_Date
) itmin
OUTER APPLY (
    SELECT End_Date = MIN(Start_Date) FROM @Items std
    WHERE std.Item_ID <> its.Item_ID+1000 AND std.Start_Date > its.Start_Date AND std.Start_Date < its.End_Date
) itmax;

Output:

id  | Start_Date                    | End_Date                      
0   | 2015-01-23 00:00:00.0000000   | 2015-01-23 00:00:00.0000000   => 1
0   | 2015-01-24 00:00:00.0000000   | 2015-01-27 00:00:00.0000000   => 4
0   | 2015-01-29 00:00:00.0000000   | 2015-01-30 00:00:00.0000000   => 2
1   | 2016-01-20 00:00:00.0000000   | 2016-01-22 00:00:00.0000000   => 3
1   | 2016-01-23 00:00:00.0000000   | 2016-01-24 00:00:00.0000000   => 2
1   | 2016-01-25 00:00:00.0000000   | 2016-01-29 00:00:00.0000000   => 5

If you use these Start Date and End Date with DATEDIFF:

SELECT DATEDIFF(day
    , its.Start_Date 
    , End_Date = COALESCE(DATEADD(day, -1, itmax.End_Date), CASE WHEN itmin.Start_Date > its.End_Date THEN itmin.Start_Date ELSE its.End_Date END)
) + 1
...

Output (with duplicates) is:

• 1, 4 and 2 for id 0 (your sample => SUM=7)
• 3, 2 and 5 for id 1 (Ypercube sample => SUM=10)

You then only need to put everything together with a SUM and GROUP BY:

SELECT id 
    , Days = SUM(
        DATEDIFF(day, Start_Date, End_Date)+1
    )
FROM (
    SELECT DISTINCT its.id
         , Start_Date = its.Start_Date 
        , End_Date = COALESCE(DATEADD(day, -1, itmax.End_Date), CASE WHEN itmin.Start_Date > its.End_Date THEN itmin.Start_Date ELSE its.End_Date END)
    FROM @Items its
    OUTER APPLY (
        SELECT Start_Date = MAX(End_Date) FROM @Items std
        WHERE std.Item_ID <> its.Item_ID AND std.Start_Date < its.Start_Date AND std.End_Date > its.Start_Date
    ) itmin
    OUTER APPLY (
        SELECT End_Date = MIN(Start_Date) FROM @Items std
        WHERE std.Item_ID <> its.Item_ID AND std.Start_Date > its.Start_Date AND std.Start_Date < its.End_Date
    ) itmax
) as d
GROUP BY id;

Output:

id  Days
0   7
1   10

Data used with 2 different ids:

INSERT INTO @Items
    (id, Item_ID, Start_Date, End_Date)
VALUES 
    (0, 20009, '2015-01-23', '2015-01-26'),
    (0, 20010, '2015-01-24', '2015-01-24'),
    (0, 20011, '2015-01-23', '2015-01-26'),
    (0, 20012, '2015-01-23', '2015-01-27'),
    (0, 20013, '2015-01-23', '2015-01-27'),
    (0, 20014, '2015-01-29', '2015-01-30'),

    (1, 20009, '2016-01-20', '2016-01-24'),
    (1, 20010, '2016-01-23', '2016-01-26'),
    (1, 20011, '2016-01-25', '2016-01-29')

Seems like you're right on the tip of the answer. Just group by the customer, the year, and then the month.

USE Masscomm_XT; 

WITH C0 AS (
  SELECT CustomerName ,Minutes. ,year(Postingdate) AS PostingYear ,month(postingdate) AS PostingMonth ,PostingDate
  FROM dbo.reptview_LDUsageTrend
)

SELECT C0.CustomerName ,C0.PostingMonth ,C0.PostingYear, SUM (Minutes) AS MinuteTotal
FROM C0
GROUP BY C0.CustomerName, C0.PostingYear, C0.PostingMonth
;