For each quarter between two dates, add rows quarter by quarter in SQL SERVER - sql

Question

I have a table, with types int, datetime, datetime:
id start date end date
-- ---------- ----------
1 2019-04-02 2020-09-17
2 2019-08-10 2020-08-10
Here is create/insert:
CREATE TABLE dbo.something
(
id int,
[start date] datetime,
[end date] datetime
);
INSERT dbo.something(id,[start date],[end date])
VALUES(1,'20190402','20200917'),(2,'20190810','20200810');
What is a SQL query that can produce these results:
id Year Quarter
-- ---- ----------
1 2019 2
1 2019 3
1 2019 4
1 2020 1
1 2020 2
1 2020 3
2 2019 3
2 2019 4
2 2020 1
2 2020 2
2 2020 3

Answer 1

Just use a recursive CTE. This version switches to counting quarters from year 0:
with cte as (
select id,
year(start_date) * 4 + datepart(quarter, start_date) - 1 as yyyyq,
year(end_date) * 4 + datepart(quarter, end_date) - 1 as end_yyyyq
from t
union all
select id, yyyyq + 1, end_yyyyq
from cte
where yyyyq < end_yyyyq
)
select id, yyyyq / 4 as year, (yyyyq % 4) + 1 as quarter
from cte;
Here is a db<>fiddle.

Answer 2

If you cannot make another reference table/etc, you can use DATEDIFF (and DATEPART) using quarters, and then some simple date arithmetic.
The logic below is simply to find, for each startdate, the first quarter and then the number of additional quarters to get to the maximum. Then do a SELECT where the additional quarters are added to the startdate, to get each quarter.
The hardest part of the query to understand imo is the WITH numberlist section - all this does is generate a series of integers between 0 and the maximum number of quarters difference. If you already have a numbers table, you can use that instead.
Key code part is below, and here's a full DB_Fiddle with some additional test data.
CREATE TABLE #yourtable (id int, startdate date, enddate date)
INSERT INTO #yourtable (id, startdate, enddate) VALUES
(1, '2019-04-02', '2020-09-17'),
(2, '2019-08-10', '2020-08-20')
; WITH number_list AS
-- list of ints from 0 to maximum number of quarters
(SELECT n
FROM (SELECT ones.n + 10*tens.n AS n
FROM (VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) ones(n),
(VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) tens(n)
) AS a
WHERE n <= (SELECT MAX(DATEDIFF(quarter,startdate,enddate)) FROM #yourtable)
)
SELECT id,
YEAR(DATEADD(quarter, number_list.n, startdate)) AS [Year],
DATEPART(quarter, DATEADD(quarter, number_list.n, startdate)) AS [Quarter]
FROM (SELECT id, startdate, DATEDIFF(quarter,startdate,enddate) AS num_additional_quarters FROM #yourtable) yt
CROSS JOIN number_list
WHERE number_list.n <= yt.num_additional_quarters
DROP TABLE #yourtable

Answer 3

First create a date dimension table which contains date, corresponding quarter and year. Then use below query to get the result. Tweak column and table name according to your schema.
with q_date as
(
select 1 as id, '2019-04-02' :: date as start_date, '2020-09-17' :: date as end_date
UNION ALL
select 2 as id, '2019-08-10' :: date as start_date, '2020-08-10' :: date as end_date
)
select qd.id, dd.calendar_year, dd.calendar_quarter_number
from dim_date dd, q_date qd
where dd.date_dmk between qd.start_date and qd.end_date
group by qd.id, dd.calendar_year, dd.calendar_quarter_number
order by qd.id, dd.calendar_year, dd.calendar_quarter_number;