Adding Missing Month in T-SQL - sql

Question

I have a data something like this:
LoanId PaymentDate PaymentMonth PaymentAmount
L1 12-01-2008 01 100
L2 15-02-2008 02 300
L3 01-04-2008 04 500
L3 01-10-2008 10 500
I want to add missing PaymentMonth's for each loanId's, like this:
LoanId PaymentYear PaymentMonth PaymentAmount
L1 2008 01 100
L1 2008 02 0
L1 2008 03 0
.. .. .. ..
L1 2008 12 0
L2 2008 01 0
L2 2008 02 300
L2 2008 03 0
.. .. .. ..
L3 2008 01 0
L3 2008 02 0
L3 2008 03 0
L3 2008 04 500
.. .. .. ..
L3 2008 10 500
.. .. .. ..
L3 2008 12 0
Was doing it manually, but now got more than 100k LoanId's from 2008-20012

Answer 1

Try to do this:
use db_test;
go
create table dbo.test1
(
loanId varchar(2),
paymentDate date,
paymentMonth varchar(2),
paymentAmount float
);
set dateformat dmy;
insert into dbo.test1
values
('L1', '12-01-2008', '01', 100),
('L2', '15-02-2008', '02', 300),
('L3', '01-04-2008', '04', 500),
('L3', '01-10-2008', '10', 500);
set dateformat ymd;
with cte as (
select cast('2008-01-31' as date) as month_dt, 1 as month_nm, format(1, 'd2') as paymentMonth
union all
select eomonth(dateadd(month, 1, month_dt)), month_nm + 1, format(month(month_dt) % 12 + 1, 'd2')
from cte
where month_dt < '2012-12-31'
), cte2 as (
select
t.loanId,
x.month_dt,
x.paymentMonth
from (
select distinct loanId from dbo.test1
) t
join cte x
on 1 = 1
)
select
a.loanId, year(a.month_dt) as paymentYear, a.paymentMonth, coalesce(b.sm, 0) as paymentAmount
from
cte2 a
left join (
select loanId, eomonth(paymentDate) as paymentDate, paymentMonth, sum(paymentAmount) as sm
from dbo.test1
group by loanId, eomonth(paymentDate), paymentMonth
) b
on a.month_dt = b.paymentDate
and a.loanId = b.loanId
order by
paymentYear asc,
loanId asc,
paymentMonth;

Answer 2

you could try like:
1.) Getting your MIN & MAX PaymentDate (as i asume those are the your ranges)
2.) Creating all months within this range - in my example with a common table expression).
3.) Finally selecting your data and joining with those month-dates and grouping the result
DECLARE #StartDate DATETIME,
#EndDate DATETIME;
SET #StartDate = SELECT MIN(PaymentDate)
FROM yourtable
SET #EndDate = SELECT MAX(PaymentDate)
FROM yourtable
;WITH CTE AS (
SELECT DATEADD(MONTH, x.number, #StartDate) as Months
FROM master.dbo.spt_values x
WHERE x.type = 'P'
AND x.number <= DATEDIFF(MONTH, #StartDate, #EndDate)
)
SELECT yourtable.LoanID
,yourtable.PaymentYear
,yourtable.PaymentMonth
,SUM(ISNULL(PaymentAmount,0)) as PaymentAmount
FROM CTE
INNER JOIN yourtable
ON yourtable.PaymentYear = CONVERT(VARCHAR(4),DATEPART(YEAR, Months))
AND yourtable.PaymentMonth = RIGHT('0' + CONVERT(VARCHAR(2),DATEPART(MONTH, Months)),2)
GROUP BY yourtable.LoanID
,yourtable.PaymentYear
,yourtable.PaymentMonth

Answer 3

This is one way of doing it, pretty straightforward. Necessary comments are in the code.
declare #LoanData table (
ID char(2),
PaymentDate date,
PaymentAmount int
)
insert into #LoanData values
('L1', '01-12-2008',100),
('L2', '02-15-2008',300),
('L3', '04-01-2008',500),
('L3', '10-01-2008',500)
declare #TableID table(id char(2))
--list of IDs
insert into #TableID select distinct ID from #LoanData
declare #PaymentMonth table(
LoanID char(2),
PaymentYear int,
PaymentMonth int,
PaymentAmount int
)
declare #month int, #year int, #i int, #id char(2)
select #i = count(*) from #TableID
--first get the table which has recotrd for every month for every id (default value in PaymentAmount is 0)
while #i > 0
begin
select top 1 #id = id from #TableID
set #year=2008
while #year <= 2012
begin
set #month=1
while #month <= 12
begin
insert into #PaymentMonth values (#id, #year, #month, 0)
set #month = #month + 1
end
set #year = #year + 1
end
delete from #TableID where id = #id
set #i = #i - 1
end
--update table based on your initial data
update #PaymentMonth
set PaymentAmount = A.PaymentAmount from #LoanData as A
where LoanID = A.ID and PaymentYear = datepart(YEAR, A.PaymentDate) and PaymentMonth = datepart(MONTH, A.PaymentDate)
select * from #PaymentMonth

Answer 4

create table temp_loantable (
loanid bigint,
paymentdate date,
paymentmonth varchar(2),
paymentamount numeric(10,2))
Having a date range ( year & month) and then doing a left outer join should get the desired output.
select * from
(select years.n yearval , months.n monthval
from (values(2008), (2009), (2010), (2011), (2012)) years(n),
(values(1),(2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12)) months(n)) a
left outer join temp_loantable l
on year(paymentdate) = a.yearval
and month(paymentdate) = a.monthval