Update Value without cursor - sql

Question

I have a table in the database.
Bill
ID Total Paid Status
1 1000 1000 Paid
2 500 400 Part Paid
3 700 0 Unpaid
4 200 0 Unpaid
Now the User pays PAID_AMT -> $900, which i want to distribute such that my table looks:
ID Total Paid Status
1 1000 1000 Paid
2 500 500 Paid
3 700 700 Paid
4 200 100 Part Paid
It can be easily done using cursor, but i want to avoid cursors.
Is it possible to achieve this using simple update queries with Output parameters.
Something like this
Update Bill
Set Paid = Total,
Status = 'Paid',
Output PAID_AMT = PAID_AMT - (Total-Paid )
where Total-Paid > PAID_AMT

Answer 1

The following query shows the amount owed, assuming SQL Server 2012:
select b.*,
sum(total - paid) over (order by id) as cumNotPaid
from bill b
You can now distribute the amount:
select b.*,
(case when cumNotPaid >= #AMOUNT then 0
when cumNotPaid - toBePaid <= #AMOUNT then toBePaid
else #AMOUNT - cumnotPaid
end) as PaidAmount
from (select b.*,
sum(total - paid) over (order by id) as cumNotPaid,
total - paid as ToBePaid
from bill b
) b
Now, this is an updatable CTE, so we can use this in an update statement:
with toupdate as (
(select b.*,
(case when cumNotPaid >= #AMOUNT then 0
when cumNotPaid - toBePaid <= #AMOUNT then toBePaid
else #AMOUNT - cumnotPaid
end) as PaidAmount
from (select b.*,
sum(total - paid) over (order by id) as cumNotPaid,
total - paid as ToBePaid
from bill b
) b
)
update toupdate
set paid = PaidAmount,
status = (case when total = paid then 'Paid' when total = 0 then 'UnPaid'
else 'PartPaid'
end);

Answer 2

I don't know what version of SQL server do you, if it 2008 then you could not use rolling sum with window function. You can try this recursive query:
declare #paid_amount int = 900
;with cte1 as (
select
b.id,
b.total - b.paid as diff,
row_number() over(order by id) as row_num
from Bill as b
where b.total <> b.paid
), cte2 as (
select
c1.id, c1.row_num, #paid_amount - c1.diff as paid_amount
from cte1 as c1
where c1.row_num = 1
union all
select
c1.id, c1.row_num, c2.paid_amount - c1.diff as paid_amount
from cte1 as c1
inner join cte2 as c2 on c2.row_num + 1 = c1.row_num
where c2.paid_amount > 0
)
update Bill set
Paid =
case
when c.paid_amount >= 0 then b.Total
else b.Total - b.Paid + c.paid_amount
end,
Status = case when c.paid_amount >= 0 then 'Paid' else 'Part Paid' end
from Bill as b
inner join cte2 as c on c.id = b.id
sql fiddle demo
for SQL server 2012 it's a bit easier:
declare #paid_amount int = 900
;with cte1 as (
select
b.id,
b.total - b.paid as amount_to_pay,
sum(b.total - b.paid) over(order by b.id) as amount
from Bill as b
where b.total <> b.paid
), cte2 as (
select
c.id,
#paid_amount - c.amount as remain_amount
from cte1 as c
where #paid_amount - c.amount + c.amount_to_pay >= 0
)
update Bill set
Paid =
case
when c.remain_amount >= 0 then b.Total
else b.Total - b.Paid + c.remain_amount
end,
Status = case when c.remain_amount >= 0 then 'Paid' else 'Part Paid' end
from Bill as b
inner join cte2 as c on c.id = b.id;
sql fiddle demo

Answer 3

If you are using SQL 2012 you can use the following:
DECLARE #PayAmount INT = 900;
WITH Dues AS
(
SELECT *, Total-Paid AS Due
FROM Bill
)
, Cumulative AS
(
SELECT *, SUM(Due) OVER (ORDER BY Id) AS CumulativeTotalDue
FROM Dues
)
, Payable AS
(
SELECT *, #PayAmount - CumulativeTotalDue AS AmountLeftAfterPaying
FROM Cumulative
)
, BillWithAmountToApplyRaw AS
(
SELECT *
, CASE
WHEN AmountLeftAfterPaying >= 0 THEN Due
ELSE Due + AmountLeftAfterPaying
END AS RawAmountToApply
FROM Payable
)
, BillWithAmountToApply AS
(
SELECT *, CASE WHEN RawAmountToApply < 0 THEN 0 ELSE RawAmountToApply END AS AmountToApply
FROM BillWithAmountToApplyRaw
)
That will give you the amount to apply in the AmountToApply column.
So you can use the above as
UPDATE BillWithAmountToApply
SET Paid = Paid + AmountToApply
FROM BillWithAmountToApply
(Use
SELECT *
FROM BillWithAmountToApply
to check it out first if you want)
SQL 2008 Version (less efficient because of the repeated joins, which aren't necessary in 2012):
WITH Dues AS
(
SELECT *, Total-Paid AS Due
FROM Bill
)
, CumulativeDue AS
(
SELECT base.Id, SUM(cumulative.Due) AS CumulativeTotalDue
FROM Dues base
JOIN Dues cumulative ON cumulative.Id <= base.Id
GROUP BY base.Id
)
, Cumulative AS
(
SELECT Dues.*, CumulativeDue.CumulativeTotalDue
FROM Dues
JOIN CumulativeDue ON CumulativeDue.Id = Dues.Id
)
... as above
Schema objects:
--BEGIN TRAN;
--CREATE TABLE Bill
--(
-- ID Int PRIMARY KEY IDENTITY,
-- Total INT NOT NULL,
-- Paid INT NOT NULL DEFAULT(0),
-- Status AS
-- CASE
-- WHEN Paid = Total THEN 'Paid'
-- WHEN Paid = 0 THEN 'Unpaid'
-- ELSE 'Part Paid'
-- END
--);
--WITH KnownValues(Total, Paid) AS
--(
-- SELECT 1000, 1000
-- UNION ALL SELECT 500, 400
-- UNION ALL SELECT 700, 0
-- UNION ALL SELECT 200, 0
--)
--INSERT INTO Bill(Total, Paid)
--SELECT *
--FROM KnownValues;
--COMMIT