Incrementing An Invoice Number

Hi there

I need a bit of generic advice about a project I am currently working on which is slightly out of my comfort zone. I€™m using SQL 2005 and VB.Net to develop an application that produces invoices for a number of different countries. The issue is that the data is arriving from an AS400 system so the tables I am working from are a little strange! This results in a fair degree of work tweaking the data into a format that is useful for my application.

To simplify the explanation each invoice in its basic form consists of the invoice data and the line items (so there is nothing new here). What is unusual is that the invoice data has an invoice number but then an additional invoice number specific to the country it is destined for. The initial invoice number arrives with the data from the AS400 but the secondary number is generated according to a number of business rules.

I have written an update query in a stored procedure which updates the invoice data with a number of values from a secondary table and a number of calculated values. There are several functions, one in particular which looks up the new invoice number from a secondary table based on specific criteria (country of destination being one of them) and I had intended to write an update query, called from within this function which then increments the invoice number but I have since found out that you cant do an update/delete from a function?

I can€™t add an update query to increment the value after the initial update query as this results in the stored procedure running through and adding all the invoice numbers (which are the same) and then the number being incremented at the end.

I assume I can€™t call an update query from within the initial update query so that the increment takes place after each loop of the initial update (if I can what would the syntax be?).

I have tried writing a trigger which completes the increment when the invoice data is updated. I haven€™t used triggers before but once again it appears as if the first update query is running through and completing all the updates and then the trigger fires incrementing the number. Or have I just got this wrong?

I guess what I need is a trigger which fires after each row of the table is updated which was how I assumed it should work!

Ironically I could write this in VB.Net with ease but for speed we need it within the database.

What is the best way to increment my invoice number?

I€™m sorry of this is general in nature but im really looking for some advice as to the best approach to deal with this issue.

Martyn Fewtrell