Split date range to year-month rows on SQL Server 2005 - sql

Question

I need to create an output where I got one row per year-month.
Assume the dataset is:
id | dateStart | dateEnd
1 | 2015-01-01 00:00:00.000 | 2015-03-31 00:00:00.000
2 | 2014-07-01 00:00:00.000 | 2014-08-31 00:00:00.000
...
I need the following output:
id | year-month
1 | 2015-01
1 | 2015-02
1 | 2015-03
2 | 2014-07
2 | 2014-08
The output can be any datatype since I can just change that later.
That is for 2015-01 the following is ok, "2015-01-01 00:00:00.000", "2015-01-01", "201501", "2015 | jan" ect.
Note I'm using SQL Server 2005.

Answer 1

Here is a method that uses recursive CTEs:
with CTE as (
select id, dateStart as dte, dateEnd
from t
union all
select id, dateadd(month, 1, dte), dateEnd
from CTE
where dateadd(month, 1, dte) < dateEnd
)
select id, dte
from CTE;
You can convert the final result into any format you like. For instance:
select id, year(dte) * 10000 + month(dte) as yyyymm_int
or
select id, cast(year(dte) * 10000 + month(dte) as varchar(255)) as yyyymm

Answer 2

Generate tally table(just make sure you get enough rows there). tally will contain values 0,1,2,.....n. Then you do a join with condition adding thise values as months to startDate until it is greater then endDate:
DECLARE #t TABLE
(
id INT ,
dateStart DATETIME ,
dateEnd DATETIME
)
INSERT INTO #t
VALUES ( 1, '2015-01-01 00:00:00.000', '2015-03-31 00:00:00.000' ),
( 2, '2014-07-01 00:00:00.000', '2014-08-31 00:00:00.000' )
;WITH cte AS(SELECT -1 + ROW_NUMBER() OVER(ORDER BY t1.m) m
FROM(VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0))t1(m) CROSS JOIN
(VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0))t2(m))
SELECT t.id,
DATEADD(mm, c.m, t.dateStart) AS year_month
FROM cte c
JOIN #t t ON DATEADD(mm, c.m, t.dateStart) <= t.dateEnd
ORDER BY t.id, year_month
Output:
id year_month
1 2015-01-01 00:00:00.000
1 2015-02-01 00:00:00.000
1 2015-03-01 00:00:00.000
2 2014-07-01 00:00:00.000
2 2014-08-01 00:00:00.000

Answer 3

In an ideal world you would have a calendar table, then your query would simply be:
SELECT t.id,
c.FirstDayOfMonth
FROM YourTable AS t
INNER JOIN dbo.Calendar c
ON c.FirstDayOfMonth >= t.DateStart
AND c.FirstDayOfMonth <= t.DateEnd
AND c.DayOfMonth = 1;
Assuming that you don't have a calendar table then you can do it with a list of numbers generated on the fly (Read this article for more on this). The following will generate a list from 1-10,000:
WITH N1 AS (SELECT N FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N (N)),
N2 (N) AS (SELECT 1 FROM N1 AS N1 CROSS JOIN N1 AS N2),
N3 (N) AS (SELECT 1 FROM N2 AS N1 CROSS JOIN N2 AS N2),
Numbers (Number) AS (SELECT ROW_NUMBER() OVER(ORDER BY N3.N) FROM N3)
SELECT * FROM Numbers;
Then you can join this to your original table:
DECLARE #T TABLE (id INT, DateStart DATE, DateEnd DATE);
INSERT #T (ID, DateStart, DateEnd)
VALUES (1, '20150101', '20150331'), (2, '20140701', '20140831');
WITH N1 AS (SELECT N FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N (N)),
N2 (N) AS (SELECT 1 FROM N1 AS N1 CROSS JOIN N1 AS N2),
N3 (N) AS (SELECT 1 FROM N2 AS N1 CROSS JOIN N2 AS N2),
Numbers (Number) AS (SELECT ROW_NUMBER() OVER(ORDER BY N3.N) FROM N3)
SELECT t.ID,
[year-month] = DATEADD(MONTH, n.Number + DATEDIFF(MONTH, 0, t.DateStart), 0)
FROM #T AS t
INNER JOIN Numbers AS N
ON N.Number - 1 <= DATEDIFF(MONTH, t.DateStart, t.DateEnd);