I have recently had several situations where I need different data from the same table. One example is where I would loop through each "delivery driver" and generate a printable PDF file for each customer they are to deliver to.
In this situation, I pulled all customers and stored them into
List<Customer> AllCustomersList = customers.GetAllCustomers();
As I looped through the delivery drivers, I'd do something like this:
List<Customer> DeliveryCustomers = AllCustomersList.Where(a => a.DeliveryDriverID == DriverID);
My question: Is the way I'm doing it by querying the List object faster than querying the database each time for customer records associated with the delivery driver?
There isn't an accurate number for amount of rows that if you pass it you should query the DB instead in in-memory
But the rule of thumb is, DB are designed to work with large amount of data and they have optimization "mechanisms" while in in-memory there aren't such things.
So you will need to benchmark it to see if the round-trip to DB is worth it for that amount of rows for each time it's important to you
"We should forget about small efficiencies, say about 97% of the time: premature
optimization is the root of all evil"