Finding records over continuous date range - sql

Question

I need to write a query which returns loans that have been taken in a semester, the semesters are defined in this way:
Jan - April - Spring
May - August - Summer
September - Dec - Fall
Now my loans can start at any time and can span for any duration of time:
say a loan starts in Dec 2013 to Oct 2014, then the loan has spanned the four semesters:
Fall 2013
Spring 2014
Summer 2014
Fall 2014
And so when counting the number of loans for each semester for each year, the count of this loan will be present in all the four semesters
Fall 2013
Spring 2014
Summer 2014
Fall 2014
The schema of the loan table is
LOAN(Loan_ID, St_id#, Comp_id#, Start_Date, Date_Returned)
where start_date and date_returned are the corresponding start and end dates of a loan.
What I have so far does not take into account loans that have overlapped into semesters.
SELECT extract(YEAR FROM start_date) AS year,
CASE WHEN extract(MONTH FROM start_date) <= 4 THEN 'spring'
WHEN extract(MONTH FROM start_date) > 4 AND extract(MONTH FROM start_date) <=8 THEN 'summer'
ELSE 'fall' END AS semester,
Count(comp_id) AS num_of_loans
FROM loan
GROUP BY (extract(YEAR FROM start_date),
CASE WHEN extract(MONTH FROM start_date) <= 4 THEN 'spring'
WHEN extract(MONTH FROM start_date) > 4 AND extract(MONTH FROM start_date) <=8 THEN 'summer'
ELSE 'fall' END)
ORDER BY YEAR, Decode(semester, 'spring', 1, 'summer', 2, 'fall', 3);
Sample Input:
INSERT INTO loan VALUES('L101', '101', 'H101', TO_DATE('2014-10-19','YYYY-MM-DD'), TO_DATE('2014-10-30','YYYY-MM-DD'));
INSERT INTO loan VALUES('L102', '102', 'H101', TO_DATE('2014-10-31','YYYY-MM-DD'), TO_DATE('2014-11-03','YYYY-MM-DD'));
INSERT INTO loan VALUES('L103', '102', 'H102', TO_DATE('2014-10-24','YYYY-MM-DD'), TO_DATE('2014-10-30','YYYY-MM-DD'));
INSERT INTO loan VALUES('L104', '101', 'H102', TO_DATE('2014-10-31','YYYY-MM-DD'), TO_DATE('2014-11-03','YYYY-MM-DD'));
INSERT INTO loan VALUES('L105', '102', 'H102', TO_DATE('2014-11-04','YYYY-MM-DD'), TO_DATE('2014-11-10','YYYY-MM-DD'));
INSERT INTO loan VALUES('L106', '103', 'N101', TO_DATE('2014-10-15','YYYY-MM-DD'), TO_DATE('2014-10-20','YYYY-MM-DD'));
INSERT INTO loan VALUES('L107', '201', 'N101', TO_DATE('2013-09-01','YYYY-MM-DD'), TO_DATE('2013-09-19','YYYY-MM-DD'));
INSERT INTO loan VALUES('L108', '201', 'N102', TO_DATE('2013-11-15','YYYY-MM-DD'), TO_DATE('2013-11-19','YYYY-MM-DD'));
INSERT INTO loan VALUES('L109', '202', 'N102', TO_DATE('2013-10-10','YYYY-MM-DD'), TO_DATE('2013-10-19','YYYY-MM-DD'));
INSERT INTO loan VALUES('L110', '202', 'N102', TO_DATE('2013-08-23','YYYY-MM-DD'), TO_DATE('2013-09-02','YYYY-MM-DD'));
INSERT INTO loan VALUES('L111', '202', 'N104', TO_DATE('2014-11-12','YYYY-MM-DD'), TO_DATE('2014-11-15','YYYY-MM-DD'));
INSERT INTO loan VALUES('L112', '203', 'N104', TO_DATE('2014-08-27','YYYY-MM-DD'), TO_DATE('2014-08-31','YYYY-MM-DD'));
INSERT INTO loan VALUES('L113', '301', 'N104', TO_DATE('2014-09-13','YYYY-MM-DD'), TO_DATE('2014-09-23','YYYY-MM-DD'));
INSERT INTO loan VALUES('L114', '301', 'N104', TO_DATE('2014-10-23','YYYY-MM-DD'), TO_DATE('2014-10-24','YYYY-MM-DD'));
INSERT INTO loan VALUES('L115', '301', 'N107', TO_DATE('2014-10-11','YYYY-MM-DD'), TO_DATE('2014-10-14','YYYY-MM-DD'));
INSERT INTO loan VALUES('L116', '302', 'N107', TO_DATE('2014-09-10','YYYY-MM-DD'), TO_DATE('2014-09-15','YYYY-MM-DD'));
INSERT INTO loan VALUES('L117', '101', 'H101', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L118', '101', 'H103', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L119', '101', 'H104', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L120', '101', 'H103', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L121', '101', 'H104', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L122', '101', 'H105', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L123', '101', 'H106', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L124', '101', 'H106', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
INSERT INTO loan VALUES('L125', '101', 'H105', TO_DATE('2014-11-19','YYYY-MM-DD'), null);
Sample Output:
SEMESTER YEARS NUM_LOANS
Spring 2013 0
Summer 2013 3
Fall 2013 5
Spring 2014 1
Summer 2014 2
Fall 2014 20
what I get:
YEAR SEMESTER NUM_OF_LOANS
2013 summer 2
2013 fall 3
2014 summer 1
2014 fall 19
Thanks!

Answer 1

Query ::
WITH FNL AS(
SELECT EXTRACT(YEAR FROM A.START_DATE) AS YEAR,B.SEMESTER AS semester,0 as num_of_loans
FROM LOAN A,(SELECT 1 SEQ,'spring' SEMESTER,0 NUM_OF_LOANS FROM DUAL
UNION ALL
SELECT 2,'summer' SEMESTER,0 num_of_loans from dual
UNION ALL
SELECT 3,'fall' SEMESTER ,0 num_of_loans FROM DUAL) b
GROUP BY B.SEMESTER,EXTRACT(YEAR FROM START_DATE)
union all
SELECT extract(YEAR FROM start_date) AS year,
CASE WHEN extract(MONTH FROM start_date) <= 4 THEN 'spring'
WHEN extract(MONTH FROM start_date) > 4 AND extract(MONTH FROM start_date) <=8 THEN 'summer'
ELSE 'fall' END AS semester,
Count(comp_id) AS num_of_loans
FROM loan
GROUP BY (extract(YEAR FROM start_date),
CASE WHEN extract(MONTH FROM start_date) <= 4 THEN 'spring'
WHEN extract(MONTH FROM start_date) > 4 AND extract(MONTH FROM start_date) <=8 THEN 'summer'
ELSE 'fall' END)
)
select year,semester,sum(num_of_loans) from fnl group by year,semester
ORDER BY YEAR, Decode(semester, 'spring', 1, 'summer', 2, 'fall', 3);
Output :
Year semester num_of_loans
2013 spring 0
2013 summer 1
2013 fall 3
2014 spring 0
2014 summer 1
2014 fall 20
i hope this helpful for you.Good Luck.. :)

Answer 2

I don't currently have an operating SQL Server available at the moment, but I believe it should look something like this:
select #min = min(start_date),
#max = max(end_date)
FROM LOAN
SELECT #minYear = YEAR(#min),
#minSem = CEILING(MONTH(#min)/4),
#maxYear = YEAR(#max),
#maxSem = CEILING(MONTH(#max)/4),
#semCount= (4-#minSem+#maxSem)+(#maxYear-#minYear-1)*3,
#i = 0
CREATE TABLE #TMP (Semester INT, Year INT, LoanCount INT)
WHILE #i < #semCount BEGIN
SELECT #curSem = (#minSem + #i)%3, -- 3 semesters per year
#curYear = #minYear + FLOOR((#minSem +#i)/3)
INSERT INTO #TMP
SELECT #curSem,
#curYear,
(SELECT COUNT * FROM LOAN
WHERE YEAR(end_date) >= #curYear
AND CEILING(MONTH(end_date)/4)>+#curSem
YEAR(start_date) <= #curYear
AND CEILING(MONTH(start_date)/4)<=#curSem) as loanCount
SELECT #i = #i + 1
END
SELECT * FROM #TMP
Hope this helps. Good Luck

Answer 3

You have to join semestrs with loans, here's a brief example:
with loan as (
-- This is your sample data
select TO_DATE('2014-10-19','YYYY-MM-DD') startdate, TO_DATE('2014-10-30','YYYY-MM-DD') datereturned from dual union all
select TO_DATE('2014-10-31','YYYY-MM-DD'), TO_DATE('2014-11-03','YYYY-MM-DD') from dual union all
select TO_DATE('2014-10-24','YYYY-MM-DD'), TO_DATE('2014-10-30','YYYY-MM-DD') from dual union all
select TO_DATE('2014-10-31','YYYY-MM-DD'), TO_DATE('2014-11-03','YYYY-MM-DD') from dual union all
select TO_DATE('2014-11-04','YYYY-MM-DD'), TO_DATE('2014-11-10','YYYY-MM-DD') from dual union all
select TO_DATE('2014-10-15','YYYY-MM-DD'), TO_DATE('2014-10-20','YYYY-MM-DD') from dual union all
select TO_DATE('2013-09-01','YYYY-MM-DD'), TO_DATE('2013-09-19','YYYY-MM-DD') from dual union all
select TO_DATE('2013-11-15','YYYY-MM-DD'), TO_DATE('2013-11-19','YYYY-MM-DD') from dual union all
select TO_DATE('2013-10-10','YYYY-MM-DD'), TO_DATE('2013-10-19','YYYY-MM-DD') from dual union all
select TO_DATE('2013-08-23','YYYY-MM-DD'), TO_DATE('2013-09-02','YYYY-MM-DD') from dual union all
select TO_DATE('2014-11-12','YYYY-MM-DD'), TO_DATE('2014-11-15','YYYY-MM-DD') from dual union all
select TO_DATE('2014-08-27','YYYY-MM-DD'), TO_DATE('2014-08-31','YYYY-MM-DD') from dual union all
select TO_DATE('2014-09-13','YYYY-MM-DD'), TO_DATE('2014-09-23','YYYY-MM-DD') from dual union all
select TO_DATE('2014-10-23','YYYY-MM-DD'), TO_DATE('2014-10-24','YYYY-MM-DD') from dual union all
select TO_DATE('2014-10-11','YYYY-MM-DD'), TO_DATE('2014-10-14','YYYY-MM-DD') from dual union all
select TO_DATE('2014-09-10','YYYY-MM-DD'), TO_DATE('2014-09-15','YYYY-MM-DD') from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null from dual union all
select TO_DATE('2014-11-19','YYYY-MM-DD'), null FROM dual
),
timescale as ( -- Timescale boundaries to build a list of semesters
select to_date ('01.01.2013', 'dd.mm.yyyy') d1, -- Start date
to_date ('01.12.2015', 'dd.mm.yyyy') d2 -- End date
from dual
),
months as ( -- List of months withing the timescale , semestr is specified for each month
select y || '*' ||
case
when m < 5 then 'Spring'
when m > 8 then 'Fall'
else 'Summer'
end s,
d d1,
add_months(d,1)-1 d2
from (
select add_months (d1, level-1) d,
extract (year from add_months (d1, level-1)) y,
extract (month from add_months (d1, level-1)) m
from timescale
connect by add_months (d1, level-2) < d2
)
),
semestr as( -- List of semesters with their boundaries, built by grouping the list of months
select s, min(d1) d1, max(d2) d2
from months
group by s
)
-- the query itself - quite easy
select s,
(select count(1) from loan where startdate <= d2 and nvl(datereturned, d1) >= d1 ) x
from semestr
order by d1