automatically renewing records when the last day of year

Question

I'm developing a c# application that consists of Document Incoming System for my police station.

In this system, variable document's contents are been saved to an SQL database. I must give them a "Document Number".

I'm achieving all of these, but i want that every years last day such as 31.12.2014, the numbers that have been given to a document like "2145" will turn to "1" at the the first day of year 01.01.2015.

So, the records must be 2014/2145. and the last days of years turns to 2015/1.

How can I achieve this?

Answer 1

You count the existing documents for the same year, then add one.

So if you want to store a document that belongs to 2013, you first count how many existing documents you have in 2013, then add one.

I can't write the sql for you, because you haven't described the data structure, but it should be simple enough using SQL COUNT, and DATEPART to retrieve only the year from a date field.