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

[Phillip Ward]

Quote

So what would be the *right* way to do this?

Not to do it at all.

This total can be calculated ("derived") from other data that you already hold, namely the values in the invoicedetails records. It's similar reasoning to why we store someone's Date of Birth and calculate their Age from it.

Create a View that calculates this total and join queries to that View whenever you need this total. Half a million invoicedetail records won't be any problem at all for your database.

Alternatively, if you really must store this [derived] total, use a Trigger to maintain it whenever any invoicedetail record is add/changed/deleted.

Regards, Phill W.