UPDATING Table Column with new Entry

Question

I am working in Oracle APEX and I want to update column in a report with a new value in the following table. The Report Query is shown in the following diagram mentioned below.

TABLE  "VENDOR_ACCOUNT" 
(  "VEN_ACCOUNTID"      NVARCHAR2(10), 
   "VEN_REGNO"          NVARCHAR2(10), 
   "VEN_TXDATE"         DATE, 
   "VEN_INVOICE_REFNO"  NVARCHAR2(10), 
   "TOTALAMOUNT"        NVARCHAR2(10), 
   "IN"                 NUMBER(10,0), 
   "OUT"                NUMBER(10,0) 
) 

SELECT "VEN_ACCOUNTID" , 
       "VEN_REGNO" , 
       "VEN_TXDATE" , 
       "VEN_INVOICE_REFNO" , 
       "TOTALAMOUNT" , 
       "IN",
       "OUT",   
       "TOTALAMOUNT"+"IN" as "CREDIT",
       "TOTALAMOUNT"-"OUT" as "DEBIT"
FROM Vendor_Account;

Required Scenario: I want to update the TotalAmount Column with Debit and Credit. The new Debit or Credit value has to be shown in the TotalBalance column on the next record.

Answer 1

You can use Oracle analyitic function LAG:

Select "VEN_ACCOUNTID" , 
        "VEN_REGNO" , 
        "VEN_TXDATE" , 
        "VEN_INVOICE_REFNO" , 
        "TOTALAMOUNT" , 
        "TOTALAMOUNT" + lag("IN",1) over (ORDER BY "VEN_ACCOUNTID")
                      - lag("OUT",1) over (ORDER BY "VEN_ACCOUNTID") AS "NEW_TOTALAMOUNT",
        "IN",
        "OUT",  
        "TOTALAMOUNT"+"IN" as "CREDIT",
        "TOTALAMOUNT"-"OUT" as "DEBIT"
FROM    Vendor_Account;

Answer 2

Select
    "VEN_ACCOUNTID" , 
    "VEN_REGNO" , 
    "VEN_TXDATE" , 
    "VEN_INVOICE_REFNO" , 
    "TOTALAMOUNT" AS "OLD_TOTALAMOUNT"
    "TOTALAMOUNT" + nvl(lag (nvl("IN",0)-nvl("OUT",0)) 
                             over (partition by "VEN_REGNO" order by "VEN_ACCOUNTID" 
                             )
                        ,0) AS "TOTALAMOUNT"
    "IN",
    "OUT",  
 from Vendor_Account;