Re: How should I initialize a header field from the sum of a detail field?

[hamid jon]

To avoid performance issues, you should not attempt to calculate the sum in the application layer. Instead, you can use a trigger to update the invoices.itemSalesAmount field whenever the invoicedetails table is modified. The trigger should calculate the sum of invoicedetails.totalLineAmount for all records where invoicedetails.historySequenceNumber = invoices.historySequenceNumber and invoicedetails.itemNumber does not begin with '/' or '&'.