how to avoid user to access same Account?

[atul gavali]

how to avoid user to access same Account from diffrent location?
e.g There are 2 person A,B.They have joint account in bank
bank balance in their a/c is 5000. there must be a 1000
Rs. in their A/C if both A,B try to withdraw money 4000
at the same time from diffrent location how to give access to one usre at time othrwise they will withdraw 8000 Rs

if anybody have solution
please send me it on my email id:
*****************

thanx in advance

[Frinavale]

It might be a good idea to implement something at a database level that returns nothing if there is not enough money to withdraw.

-Frinny

[atul gavali]

Thanx but person B tries to withdraw amount before update
balance in their A/c. Both user has simaltenous access

will you please suggest me some code


****
Atul

[Frinavale]

What database management system are you using?
I honestly think that this is best handled at the database level.

-Frinny

[Hiren vadhiya]

Well, You have to lock the table while User A is updating the value so once A is done then table is available for reading and B will get latest value.

[atul gavali]

sql server 2005

[ck9663]

It's called concurrency. Here, start from this...

Good Luck!!!

~~ CK

[NeoPa]

Without wishing to distract you from reading the excellent piece linked by CK, one important basic point is to ensure that the checking of the available value, or current balance, is done at the point of attempted removal of funds, rather than simply checking prior to confirmation of the desire to update the balance. This can be done also, so that the operator knows not even to attempt the transaction, but this shouldn't be relied upon as there is obviously the possibility that the funds will have been removed between the time it was last checked and the confirmation of the desire to remove the funds is sent.

To put it into more standard SQL terms, it might go something like :

UPDATE [tblFunds]
SET    [Value] = [Value] - 4000
WHERE  ([ID] = {ClientID})
  AND  ([Value] >= 4000)