My first rule is performance. If you have millions of records, summing data can be long!


>I'm doing my first app related to debits and credits. What I was wondering was if it is a bad idea to keep a seperate field for all clienst that is essentially their current balance. I know a rule of thumb with databases is don't store anything that can be calculated from other data but I am wondering if it is worth it to do calcualtions from the entire table every time a balance is required. Is it so bad to do 2 transactions: one to insert the transaction and a second to +/- the balance in the client file? Just looking for comments and prior experience here. Thanks.