grouping in sql server with for xml - sql-server

Question

I have a table in the following format
reporting_date interest_payment balance
200401 10 10
200402 20 15
200403 30 20
200404 40 30
200405 50 40
200406 60 50
200407 70 60
i wanted to generate an OUTPUT in the following format :
The output of the query should look like this :
reporting_date interest_payment balance
Q1 -2004 60 10
Q2 -2004 150 30
Q3 -2004 70 60
Q4 -2004 0 0
i.e i wanted to represent data by quarter and year and group by quarter and year for interest_payment column but for balance i need to pick up the value from the first reporting date in that quarter ,so as you can see q1-2004 has 10,15 and 20 but only 10 is accounted as that was the first reporting date in that quarter
I have my query working for interest payment but i am not sure how do i pickup the first reporting value for balance in a quarter
SELECT report_year as "#date",'Q'+CAST(report_quarter+1 as varchar(1)) as "#quarter", SUM(a.balance) as "#balance", SUM(a.interest_payment) as "#interest_payment"
FROM (SELECT *,
(reporting_date%100 - 1)/3 as report_quarter,
reporting_date/100 as report_year
FROM employee) a
GROUP by report_year, report_quarter
order by report_year, report_quarter

Answer 1

First, create all combination of years and quarters. Then use window functions such AS SUM OVER() and ROW_NUMBER() for the interest_payment and balance.
CREATE TABLE #temp(
reporting_date INT,
interest_payment INT,
balance INT
)
INSERT INTO #temp VALUES
(200401, 10, 10), (200402, 20, 15), (200403, 30, 20),
(200404, 40, 30), (200405, 50, 40), (200406, 60, 50),
(200407, 70, 60);
;WITH quarters(yr, qtr) AS(
SELECT
y.N, q.N
FROM(
SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4
) q(N)
CROSS JOIN(
SELECT DISTINCT reporting_date / 100 FROM #temp
) y(N)
)
,GroupedByQtr AS(
SELECT
*,
qtr = (reporting_date % 100 -1) / 3 + 1,
yr = reporting_date / 100,
ss = SUM(interest_payment) OVER(PARTITION BY (reporting_date / 100), ((reporting_date % 100 -1) / 3 + 1)),
rn = ROW_NUMBER() OVER(PARTITION BY (reporting_date / 100), ((reporting_date % 100 -1) / 3 + 1) ORDER BY reporting_date)
FROM #temp
)
SELECT
reporting_date = 'Q' + CONVERT(VARCHAR(1), q.qtr) + ' - ' + CONVERT(VARCHAR(4), q.yr),
interest_payment = ISNULL(g.ss, 0),
balance = ISNULL(g.balance, 0)
FROM quarters q
LEFT JOIN GroupedByQtr g
ON g.qtr = q.qtr
AND g.yr = q.yr
AND g.rn = 1
RESULT
reporting_date interest_payment balance
-------------- ---------------- -----------
Q1 - 2004 60 10
Q2 - 2004 150 30
Q3 - 2004 70 60
Q4 - 2004 0 0