Replacing a set of entries with a new set of entries

[arzoo400]

I'm having trouble figuring out how to replace a set of rows with a new set of rows.

I'm doing inventory management and need to record new purchases, deliveries and returned items. My issue comes in when any of the receipts (new items, delivery or returned items) are modified.

Each of the receipts contain x number of rows of QTY and ITEM. When the user needs to modify the contents of a receipt, what is the best way to replace the old QTY and ITEMS with the new QTY and ITEMS?

My additional issues are when the # of rows of the original set of items aren't the same with the new # of rows, and when the ITEMS aren't the same.

[dagon]

while without examples of your data it is hard to tell, it does sounds like your using a non-normalised structure, and are finding out the hard way why that is a bad idea.

[johanafm]

Actually it sounds to me as if he does have normalized data, since he is talking about rows: one table for receipt and one for receipt rows, where the latter specifies item and quantity for each item on the receipt. But, there is little data to go on.
The simplest way would be to delete the old set of receipt items and insert the new set, since it sounds like some items might be taken off the list completey. Another way would be to keep track of the receipt item ids before and after change, delete those that are no longer present, update those that are still present and insert any new items. However, I doubt you'd gain performance by doing this.