subtract and add between columns and rows - sql

Question

I have some data look like this
id date total amount adj amount
1 2017-01-02 100 50
1 2017-01-02 50 0
2 2017-01-15 100 35
2 2017-01-15 35 0
3 2017-01-30 120 50
3 2017-01-30 -120 -50
3 2017-01-30 100 50
3 2017-01-30 50 0
3 2017-01-30 60 40
the output should look like, I have no clue how to do the subtraction between rows and columns.
id date due amount
1 2017-01-02 0
2 2017-01-15 0
3 2017-01-30 40
here is my current code, but it only works on maybe 1 and 2 but definitely not working for 3.
the logic for this part is to find the due amount between each entry for each id. for example, id 1 has two entry, total amount 100, then he paid 50, so the adj amount is 50, and the second entry, the total amount is 50, he paid 50, te adj amount is 0. so id 1 due amount is 0 in the end.
id 3 who has 5 entries, first there is entry show the total amount for ID 3 is 120 and he paid 70, so the adj amount is 50, but the first entry is a mistake, so all amount revised. then the third entry shows the total amount is 100, ID 3 paid 50, so the adj amount is 50. then the fourth entry shows the total amount is 50, ID 3 also paid 50, so the adj amount is 0. and the fifth entry shows that the total amount is 60, and ID 3 paid 20, so the adj amount is 40. so in final, ID 3 due amount is 40;
select distinct a.id,
a.date,
case when a.date=b.date and a.total_amount = b.adj_amount then a.adj_amount
when a.date=b.date and a.total_amount <> b.adj_amount then ABS(a.adj_amount + b.adj_amount)
else a.adj_amount
end as due_amount
from table a,
table b
where a.id=b.id;
I just wonder if there has any function which can do this kind of calculation between rows and columns.

Answer 1

Use GROUP BY and SUM().
SELECT the_date, SUM(due_amount)
FROM tab
GROUP BY the_date;

Answer 2

Something like this could work - if the transactions can be ordered. Note that I've renamed some of the columns to help clarify their meaning. I've also added a trans_seq_num column to indicate the order of a customer's transactions on a particular date. I think you're looking for the amount that the customer still owes as of their last payment.
WITH sample (id, trans_seq_num, some_date, starting_balance, ending_balance) AS
(
SELECT '1',1,'2017-01-02','100','50' FROM dual UNION ALL
SELECT '1',2,'2017-01-02','50','0' FROM dual UNION ALL
SELECT '2',1,'2017-01-15','35','0' FROM dual UNION ALL
SELECT '2',2,'2017-01-15','100','35' FROM dual UNION ALL
SELECT '3',1,'2017-01-30','120','50' FROM dual UNION ALL
SELECT '3',2,'2017-01-30','-120','-50' FROM dual UNION ALL
SELECT '3',3,'2017-01-30','100','50' FROM dual UNION ALL
SELECT '3',4,'2017-01-30','50','0' FROM dual UNION ALL
SELECT '3',5,'2017-01-30','60','40' FROM dual
)
SELECT DISTINCT id,
some_date,
LAST_VALUE(ending_balance) OVER (PARTITION BY id ORDER BY trans_seq_num RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) day_balance
FROM sample
ORDER BY 1,2,3;
ID SOME_DATE AMOUNT_DUE
----- --------------- ---------------
1 2017-01-02 0
2 2017-01-15 35
3 2017-01-30 40

Answer 3

The others already said: you should have any way of numbering rows. Simple sequence will do the job. With such unique column solution is trivial, we only find last row for each id.
But you have no order. Here is my try which looks OK so far and may temporary help:
with q as (
select table_a.*,
row_number() over (partition by id, date_, total_amount, adj_amount
order by null) rn
from table_a),
t as (
select a.*,
row_number() over (partition by id, date_, total_amount
order by null) r1,
row_number() over (partition by id, date_, adj_amount
order by null) r2
from q a
where not exists (
select 1 from q b
where a.id = b.id and a.date_ = b.date_ and a.rn = b.rn
and a.total_amount = -b.total_amount and a.adj_amount = -b.adj_amount))
select id, date_, max(adj_amount) due
from t
where connect_by_isleaf = 1
connect by prior id = id and prior date_ = date_
and prior adj_amount = total_amount and prior r2 = r1
group by id, date_;
dbfiddle
First I eliminate mistakes. Subquery t does this, it is simple not exists with added row_number to handle properly multiple cases ( like (120, 50) => (-120, -50) and again (120, 50) ).
Data is cleared so we can recursively find connected rows by previous adj_amount = total_amount. We have to use row_numbers again to handle identical rows (60, 40) => (40, 0) => (60, 40) again.
Then only leaves are taken and finally max value of these leaves which should contain orphaned non zero value if such exists for each id. You can add connect_by_path() clause to see if connection works properly.
Hierarchical queries are slower than others, so if your table is big, be warned. Filter data at first, if needed.
This query works for your examples and some others which I imagined and tested. But even if it works you should add ordering column (if possible) and have guaranteed, simple way to obtain correct results.