Banking Transaction in SQL - sql

Question

I have a table named BankTransaction:
Create table BankTransaction
(
TransactionID int IDENTITY(1,1),
AccountNumber varchar(25) Not Null,
TransactionDate datetime not null Default getdate(),
TransactionType varchar(25) Not Null,
TransactionAmount money Default '0',
BalanceAsOf money Default '0' ,
Primary Key(TransactionID)
);
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('123AABDF','Credit','22535.215');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('123AABDF','Debit','215.9');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2256DF','Credit','500');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2256DF','Debit','100');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2351AV','Credit','5000');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2351AV','Debit','100');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('123AABDF','Debit','235.215');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2256DF','Credit','1000');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2351AV','Credit','500');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('7865HNH','Credit','982000');
what I want is that The account having same AccountNumber if the TransactionType is Debit then subtract from BalanceAsOf and if the TransactionType is Credit then adding to BalanceAsOF:
This is what I tried but doesn't work:
update bt
Set BalanceAsOF = case
when AccountNumber=AccountNumber and TransactionType = 'Credit'
then ( BalanceAsOf + TransactionAmount )
when AccountNumber=AccountNumber AND TransactionType='Debit'
then BalanceAsOf - TransactionAmount
End
from
dbo.BankTransaction as bt
Select * From dbo.BankTransaction as p

Answer 1

This is exactly what you should do
set nocount on;
Create table BankTransaction
(
TransactionID int IDENTITY(1,1),
AccountNumber varchar(25) Not Null,
TransactionDate datetime not null Default getdate(),
TransactionType varchar(25) Not Null,
TransactionAmount money Default '0',
BalanceAsOf money Default '0' ,
Primary Key(TransactionID)
);
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('123AABDF','Credit','22535.215');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('123AABDF','Debit','215.9');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2256DF','Credit','500');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2256DF','Debit','100');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2351AV','Credit','5000');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2351AV','Debit','100');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('123AABDF','Debit','235.215');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2256DF','Credit','1000');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('2351AV','Credit','500');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('7865HNH','Credit','982000');
Insert into dbo.BankTransaction(AccountNumber,TransactionType,TransactionAmount)
Values ('876YYT','Credit','27363647');
Create Table #AccountNomber (
AccountNumber varchar(25) Not Null,);
insert into #AccountNomber ( AccountNumber)
Select Distinct BT.AccountNumber
From dbo.BankTransaction as BT
--select * from #AccountNomber
Declare #PreviousBalance money
Set #PreviousBalance = 0
declare #AcctNumber varchar(25)
declare #TransactionId int
--update b
--set b.BalanceAsOf=0
--from BankTransaction b
while exists(select 1 from #AccountNomber)
begin
select #AcctNumber = a.AccountNumber from #AccountNomber a
--select 'test',* from BankTransaction b
--where b.AccountNumber=#AcctNumber
--and b.BalanceAsOf=0
--order by b.TransactionID
--/*
while exists (select 1 from BankTransaction b where b.AccountNumber=#AcctNumber
and b.BalanceAsOf=0
)
begin
select #TransactionId = (select top 1 b.TransactionID from BankTransaction b
where b.AccountNumber=#AcctNumber
and b.BalanceAsOf=0
order by b.TransactionID)
select #PreviousBalance =#PreviousBalance + case when b.TransactionType='Credit' then b.TransactionAmount else -1*b.TransactionAmount end
from BankTransaction b
Where b.AccountNumber=#AcctNumber
and b.TransactionID=#TransactionId
update b
set b.BalanceAsOf=#PreviousBalance
from BankTransaction b
Where b.AccountNumber=#AcctNumber
and b.TransactionID=#TransactionId
end
select #PreviousBalance =0
delete a from #AccountNomber a
where a.AccountNumber=#AcctNumber
End
select * from BankTransaction b
order by b.TransactionID
Drop table BankTransaction
drop table #AccountNomber

Answer 2

Is there a reason to store the current Balance for each transaction? If you just want to display the balance to user you can have a column in Accounts table for example and for every transaction (insert into BankTransaction) you update this column via trigger on BankTransaction or through your application.
UPDATE
Use a trigger to calculate the balance before inserting the new transaction
CREATE TRIGGER trig_UpdBalance
ON [BankTransaction]
INSTEAD OF INSERT
AS
BEGIN
INSERT INTO BankTransaction
AccountNumber,
TransactionType,
TransactionAmount,
BalanceAsOf
SELECT
i.AccountNumber,
i.TransactionType,
i.TransactionAmount,
CASE
WHEN i.TransactionType = 'Credit'
THEN ( bt.BalanceAsOf + i.TransactionAmount )
WHEN i.TransactionType='Debit'
THEN bt.BalanceAsOf - i.TransactionAmount
END
FROM Inserted i
INNER JOIN BankTransaction bt
ON BT.AccountNumber = i.AccountNumber
AND TransactionID = (SELECT MAX(TransactionID)
FROM BankTransaction
WHERE AccountNumber = i.AccountNumber)
END