Question

I need to find the remaining amount for each credit no. The expected result is this:

CREDIT_NO   CREDIT_TYPE CREDIT_AMOUNT   TOTAL_A REMAINING_AMT   FINAL_TOTAL_PER_BILL
A1          W           100             1000     900            600
A1          X           100             1000     800            600
A1          Y           100             1000     700            600
A1          Z           100             1000     600            600
B1          X           100             2000     1900           1700
B1          Y           100             2000     1800           1700
B1          Z           100             2000     1700           1700

Here’s the query I have done so far (please pardon the noob):

WITH TEMP AS
  (SELECT 1 ID,
    'A1' CREDIT_NO,
    'X' CREDIT_TYPE,
    100 CREDIT_AMOUNT,
    1000 TOTAL_A
  FROM DUAL
  UNION ALL
  SELECT 2, 'A1' , 'Y', 100, 1000 FROM DUAL
  UNION ALL
  SELECT 4, 'A1' , 'Z', 100, 1000 FROM DUAL
  UNION ALL
  SELECT 3, 'B1', 'X', 100, 2000 FROM DUAL
  UNION ALL
  SELECT 5, 'B1', 'Y', 100, 2000 FROM DUAL
  UNION ALL
  SELECT 6, 'B1', 'Z', 100, 2000 FROM DUAL
  UNION ALL
  SELECT 7, 'A1', 'W', 100, 1000 FROM DUAL
  )

SELECT 
  TEMP1.CREDIT_NO ,
  TEMP1.CREDIT_TYPE,
  TEMP1.CREDIT_AMOUNT ,
  TEMP1.TOTAL_A ,
  CASE
    WHEN TEMP1.CREDIT_NO  = (LAG (TEMP1.CREDIT_NO,1) OVER (ORDER BY TEMP1.CREDIT_NO) ) -- set remaining CREDIT_AMOUNT
    OR (LAG (TEMP1.CREDIT_NO,1) OVER (ORDER BY TEMP1.CREDIT_NO) ) IS NULL
    THEN TEMP1.TOTAL_A - (SUM(TEMP1.CREDIT_AMOUNT) OVER ( ORDER BY TEMP1.CREDIT_NO ROWS BETWEEN
      UNBOUNDED PRECEDING
    AND CURRENT ROW ) )
    WHEN TEMP1.CREDIT_NO <>   -- new bill, new total CREDIT_AMOUNT
      (LAG (TEMP1.CREDIT_NO,1) OVER (ORDER BY TEMP1.CREDIT_NO) )
    THEN TEMP1.TOTAL_A - TEMP1.CREDIT_AMOUNT
  END AS REMAINING_AMT 
  ,TEMP1.TOTAL_A - (SUM(TEMP1.CREDIT_AMOUNT) OVER (PARTITION BY CREDIT_NO)) AS FINAL_TOTAL_PER_BILL
FROM TEMP TEMP1
ORDER BY CREDIT_NO, CREDIT_TYPE

My problem is I don’t know how to compute for the remaining amount for the 2nd credit no. The result of the above query is:

CREDIT_NO   CREDIT_TYPE CREDIT_AMOUNT   TOTAL_A REMAINING_AMT   FINAL_TOTAL_PER_BILL
A1          W           100             1000     900            600
A1          X           100             1000     800            600
A1          Y           100             1000     700            600
A1          Z           100             1000     600            600
B1          X           100             2000     1900           1700
B1          Y           100             2000     1400           1700
B1          Z           100             2000     1300           1700

Is it possible to get a running remaining amount without using a stored procedure? I tried basing it on the rownum but it is not sequential.

Even though I have found similar questions to this (Link 1, Link 2, Link 3)
(I’m still going over the third link though), I hope you guys can help me.

Answer 1

use a running subtotal, and be careful at partition clause as:

select credit_no, credit_type, 
   total_a - sum(credit_amount) over (partition by credit_no order by id) as remaining_credit,
   total_a,
   total_a - sum(credit_amount) over (partition by credit_no) as FINAL_TOTAL_PER_BILL
from temp 

see sqlfiddle